diff --git a/tests/test_vec_envs.py b/tests/test_vec_envs.py
new file mode 100644
index 0000000..2147e78
--- /dev/null
+++ b/tests/test_vec_envs.py
@@ -0,0 +1,326 @@
+import collections
+import functools
+import itertools
+import multiprocessing
+
+import pytest
+import gym
+import numpy as np
+
+from torchy_baselines.common.vec_env import DummyVecEnv, SubprocVecEnv, VecNormalize, VecFrameStack
+
+N_ENVS = 3
+VEC_ENV_CLASSES = [DummyVecEnv, SubprocVecEnv]
+VEC_ENV_WRAPPERS = [None, VecNormalize, VecFrameStack]
+
+
+class CustomGymEnv(gym.Env):
+    def __init__(self, space):
+        """
+        Custom gym environment for testing purposes
+        """
+        self.action_space = space
+        self.observation_space = space
+        self.current_step = 0
+        self.ep_length = 4
+
+    def reset(self):
+        self.current_step = 0
+        self._choose_next_state()
+        return self.state
+
+    def step(self, action):
+        reward = 1
+        self._choose_next_state()
+        self.current_step += 1
+        done = self.current_step >= self.ep_length
+        return self.state, reward, done, {}
+
+    def _choose_next_state(self):
+        self.state = self.observation_space.sample()
+
+    def render(self, mode='human'):
+        pass
+
+    @staticmethod
+    def custom_method(dim_0=1, dim_1=1):
+        """
+        Dummy method to test call to custom method
+        from VecEnv
+
+        :param dim_0: (int)
+        :param dim_1: (int)
+        :return: (np.ndarray)
+        """
+        return np.ones((dim_0, dim_1))
+
+
+@pytest.mark.parametrize('vec_env_class', VEC_ENV_CLASSES)
+@pytest.mark.parametrize('vec_env_wrapper', VEC_ENV_WRAPPERS)
+def test_vecenv_custom_calls(vec_env_class, vec_env_wrapper):
+    """Test access to methods/attributes of vectorized environments"""
+    def make_env():
+        return CustomGymEnv(gym.spaces.Box(low=np.zeros(2), high=np.ones(2)))
+    vec_env = vec_env_class([make_env for _ in range(N_ENVS)])
+
+    if vec_env_wrapper is not None:
+        if vec_env_wrapper == VecFrameStack:
+            vec_env = vec_env_wrapper(vec_env, n_stack=2)
+        else:
+            vec_env = vec_env_wrapper(vec_env)
+
+    env_method_results = vec_env.env_method('custom_method', 1, indices=None, dim_1=2)
+    setattr_results = []
+    # Set current_step to an arbitrary value
+    for env_idx in range(N_ENVS):
+        setattr_results.append(vec_env.set_attr('current_step', env_idx, indices=env_idx))
+    # Retrieve the value for each environment
+    getattr_results = vec_env.get_attr('current_step')
+
+    assert len(env_method_results) == N_ENVS
+    assert len(setattr_results) == N_ENVS
+    assert len(getattr_results) == N_ENVS
+
+    for env_idx in range(N_ENVS):
+        assert (env_method_results[env_idx] == np.ones((1, 2))).all()
+        assert setattr_results[env_idx] is None
+        assert getattr_results[env_idx] == env_idx
+
+    # Call env_method on a subset of the VecEnv
+    env_method_subset = vec_env.env_method('custom_method', 1, indices=[0, 2], dim_1=3)
+    assert (env_method_subset[0] == np.ones((1, 3))).all()
+    assert (env_method_subset[1] == np.ones((1, 3))).all()
+    assert len(env_method_subset) == 2
+
+
+    # Test to change value for all the environments
+    setattr_result = vec_env.set_attr('current_step', 42, indices=None)
+    getattr_result = vec_env.get_attr('current_step')
+    assert setattr_result is None
+    assert getattr_result == [42 for _ in range(N_ENVS)]
+
+    # Additional tests for setattr that does not affect all the environments
+    vec_env.reset()
+    setattr_result = vec_env.set_attr('current_step', 12, indices=[0, 1])
+    getattr_result = vec_env.get_attr('current_step')
+    getattr_result_subset = vec_env.get_attr('current_step', indices=[0, 1])
+    assert setattr_result is None
+    assert getattr_result == [12 for _ in range(2)] + [0 for _ in range(N_ENVS - 2)]
+    assert getattr_result_subset == [12, 12]
+    assert vec_env.get_attr('current_step', indices=[0, 2]) == [12, 0]
+
+    vec_env.reset()
+    # Change value only for first and last environment
+    setattr_result = vec_env.set_attr('current_step', 12, indices=[0, -1])
+    getattr_result = vec_env.get_attr('current_step')
+    assert setattr_result is None
+    assert getattr_result == [12] + [0 for _ in range(N_ENVS - 2)] + [12]
+    assert vec_env.get_attr('current_step', indices=[-1]) == [12]
+
+    vec_env.close()
+
+
+class StepEnv(gym.Env):
+    def __init__(self, max_steps):
+        """Gym environment for testing that terminal observation is inserted
+        correctly."""
+        self.action_space = gym.spaces.Discrete(2)
+        self.observation_space = gym.spaces.Box(np.array([0]), np.array([999]),
+                                                dtype='int')
+        self.max_steps = max_steps
+        self.current_step = 0
+
+    def reset(self):
+        self.current_step = 0
+        return np.array([self.current_step], dtype='int')
+
+    def step(self, action):
+        prev_step = self.current_step
+        self.current_step += 1
+        done = self.current_step >= self.max_steps
+        return np.array([prev_step], dtype='int'), 0.0, done, {}
+
+
+@pytest.mark.parametrize('vec_env_class', VEC_ENV_CLASSES)
+@pytest.mark.parametrize('vec_env_wrapper', VEC_ENV_WRAPPERS)
+def test_vecenv_terminal_obs(vec_env_class, vec_env_wrapper):
+    """Test that 'terminal_observation' gets added to info dict upon
+    termination."""
+    step_nums = [i + 5 for i in range(N_ENVS)]
+    vec_env = vec_env_class([functools.partial(StepEnv, n) for n in step_nums])
+
+    if vec_env_wrapper is not None:
+        if vec_env_wrapper == VecFrameStack:
+            vec_env = vec_env_wrapper(vec_env, n_stack=2)
+        else:
+            vec_env = vec_env_wrapper(vec_env)
+
+    zero_acts = np.zeros((N_ENVS,), dtype='int')
+    prev_obs_b = vec_env.reset()
+    for step_num in range(1, max(step_nums) + 1):
+        obs_b, _, done_b, info_b = vec_env.step(zero_acts)
+        assert len(obs_b) == N_ENVS
+        assert len(done_b) == N_ENVS
+        assert len(info_b) == N_ENVS
+        env_iter = zip(prev_obs_b, obs_b, done_b, info_b, step_nums)
+        for prev_obs, obs, done, info, final_step_num in env_iter:
+            assert done == (step_num == final_step_num)
+            if not done:
+                assert 'terminal_observation' not in info
+            else:
+                terminal_obs = info['terminal_observation']
+
+                # do some rough ordering checks that should work for all
+                # wrappers, including VecNormalize
+                assert np.all(prev_obs < terminal_obs)
+                assert np.all(obs < prev_obs)
+
+                if not isinstance(vec_env, VecNormalize):
+                    # more precise tests that we can't do with VecNormalize
+                    # (which changes observation values)
+                    assert np.all(prev_obs + 1 == terminal_obs)
+                    assert np.all(obs == 0)
+
+        prev_obs_b = obs_b
+
+    vec_env.close()
+
+
+SPACES = collections.OrderedDict([
+    ('discrete', gym.spaces.Discrete(2)),
+    ('multidiscrete', gym.spaces.MultiDiscrete([2, 3])),
+    ('multibinary', gym.spaces.MultiBinary(3)),
+    ('continuous', gym.spaces.Box(low=np.zeros(2), high=np.ones(2))),
+])
+
+def check_vecenv_spaces(vec_env_class, space, obs_assert):
+    """Helper method to check observation spaces in vectorized environments."""
+    def make_env():
+        return CustomGymEnv(space)
+
+    vec_env = vec_env_class([make_env for _ in range(N_ENVS)])
+    obs = vec_env.reset()
+    obs_assert(obs)
+
+    dones = [False] * N_ENVS
+    while not any(dones):
+        actions = [vec_env.action_space.sample() for _ in range(N_ENVS)]
+        obs, _rews, dones, _infos = vec_env.step(actions)
+        obs_assert(obs)
+    vec_env.close()
+
+
+def check_vecenv_obs(obs, space):
+    """Helper method to check observations from multiple environments each belong to
+       the appropriate observation space."""
+    assert obs.shape[0] == N_ENVS
+    for value in obs:
+        assert space.contains(value)
+
+
+@pytest.mark.parametrize('vec_env_class,space', itertools.product(VEC_ENV_CLASSES, SPACES.values()))
+def test_vecenv_single_space(vec_env_class, space):
+    def obs_assert(obs):
+        return check_vecenv_obs(obs, space)
+
+    check_vecenv_spaces(vec_env_class, space, obs_assert)
+
+
+class _UnorderedDictSpace(gym.spaces.Dict):
+    """Like DictSpace, but returns an unordered dict when sampling."""
+    def sample(self):
+        return dict(super().sample())
+
+
+@pytest.mark.parametrize('vec_env_class', VEC_ENV_CLASSES)
+def test_vecenv_dict_spaces(vec_env_class):
+    """Test dictionary observation spaces with vectorized environments."""
+    space = gym.spaces.Dict(SPACES)
+
+    def obs_assert(obs):
+        assert isinstance(obs, collections.OrderedDict)
+        assert obs.keys() == space.spaces.keys()
+        for key, values in obs.items():
+            check_vecenv_obs(values, space.spaces[key])
+
+    check_vecenv_spaces(vec_env_class, space, obs_assert)
+
+    unordered_space = _UnorderedDictSpace(SPACES)
+    # Check that vec_env_class can accept unordered dict observations (and convert to OrderedDict)
+    check_vecenv_spaces(vec_env_class, unordered_space, obs_assert)
+
+
+@pytest.mark.parametrize('vec_env_class', VEC_ENV_CLASSES)
+def test_vecenv_tuple_spaces(vec_env_class):
+    """Test tuple observation spaces with vectorized environments."""
+    space = gym.spaces.Tuple(tuple(SPACES.values()))
+
+    def obs_assert(obs):
+        assert isinstance(obs, tuple)
+        assert len(obs) == len(space.spaces)
+        for values, inner_space in zip(obs, space.spaces):
+            check_vecenv_obs(values, inner_space)
+
+    return check_vecenv_spaces(vec_env_class, space, obs_assert)
+
+
+def test_subproc_start_method():
+    start_methods = [None]
+    # Only test thread-safe methods. Others may deadlock tests! (gh/428)
+    safe_methods = {'forkserver', 'spawn'}
+    available_methods = multiprocessing.get_all_start_methods()
+    start_methods += list(safe_methods.intersection(available_methods))
+    space = gym.spaces.Discrete(2)
+
+    def obs_assert(obs):
+        return check_vecenv_obs(obs, space)
+
+    for start_method in start_methods:
+        vec_env_class = functools.partial(SubprocVecEnv, start_method=start_method)
+        check_vecenv_spaces(vec_env_class, space, obs_assert)
+
+    with pytest.raises(ValueError, match="cannot find context for 'illegal_method'"):
+        vec_env_class = functools.partial(SubprocVecEnv, start_method='illegal_method')
+        check_vecenv_spaces(vec_env_class, space, obs_assert)
+
+
+class CustomWrapperA(VecNormalize):
+    def __init__(self, venv):
+        VecNormalize.__init__(self, venv)
+        self.var_a = 'a'
+
+
+class CustomWrapperB(VecNormalize):
+    def __init__(self, venv):
+        VecNormalize.__init__(self, venv)
+        self.var_b = 'b'
+
+    def func_b(self):
+        return self.var_b
+
+    def name_test(self):
+        return self.__class__
+
+class CustomWrapperBB(CustomWrapperB):
+    def __init__(self, venv):
+        CustomWrapperB.__init__(self, venv)
+        self.var_bb = 'bb'
+
+def test_vecenv_wrapper_getattr():
+    def make_env():
+        return CustomGymEnv(gym.spaces.Box(low=np.zeros(2), high=np.ones(2)))
+    vec_env = DummyVecEnv([make_env for _ in range(N_ENVS)])
+    wrapped = CustomWrapperA(CustomWrapperBB(vec_env))
+    assert wrapped.var_a == 'a'
+    assert wrapped.var_b == 'b'
+    assert wrapped.var_bb == 'bb'
+    assert wrapped.func_b() == 'b'
+    assert wrapped.name_test() == CustomWrapperBB
+
+    double_wrapped = CustomWrapperA(CustomWrapperB(wrapped))
+    dummy = double_wrapped.var_a  # should not raise as it is directly defined here
+    with pytest.raises(AttributeError):  # should raise due to ambiguity
+        dummy = double_wrapped.var_b
+    with pytest.raises(AttributeError):  # should raise as does not exist
+        dummy = double_wrapped.nonexistent_attribute
+    del dummy  # keep linter happy
diff --git a/tests/test_vec_normalize.py b/tests/test_vec_normalize.py
new file mode 100644
index 0000000..fbcee54
--- /dev/null
+++ b/tests/test_vec_normalize.py
@@ -0,0 +1,41 @@
+import gym
+import numpy as np
+
+from torchy_baselines.common.running_mean_std import RunningMeanStd
+from torchy_baselines.common.vec_env.dummy_vec_env import DummyVecEnv
+from torchy_baselines.common.vec_env.vec_normalize import VecNormalize
+
+ENV_ID = 'Pendulum-v0'
+
+
+def test_runningmeanstd():
+    """Test RunningMeanStd object"""
+    for (x_1, x_2, x_3) in [
+        (np.random.randn(3), np.random.randn(4), np.random.randn(5)),
+        (np.random.randn(3, 2), np.random.randn(4, 2), np.random.randn(5, 2))]:
+        rms = RunningMeanStd(epsilon=0.0, shape=x_1.shape[1:])
+
+        x_cat = np.concatenate([x_1, x_2, x_3], axis=0)
+        moments_1 = [x_cat.mean(axis=0), x_cat.var(axis=0)]
+        rms.update(x_1)
+        rms.update(x_2)
+        rms.update(x_3)
+        moments_2 = [rms.mean, rms.var]
+
+        assert np.allclose(moments_1, moments_2)
+
+
+def test_vec_env():
+    """Test VecNormalize Object"""
+
+    def make_env():
+        return gym.make(ENV_ID)
+
+    env = DummyVecEnv([make_env])
+    env = VecNormalize(env, norm_obs=True, norm_reward=True, clip_obs=10., clip_reward=10.)
+    _, done = env.reset(), [False]
+    obs = None
+    while not done[0]:
+        actions = [env.action_space.sample()]
+        obs, _, done, _ = env.step(actions)
+    assert np.max(obs) <= 10
diff --git a/torchy_baselines/common/running_mean_std.py b/torchy_baselines/common/running_mean_std.py
new file mode 100644
index 0000000..d6a03d6
--- /dev/null
+++ b/torchy_baselines/common/running_mean_std.py
@@ -0,0 +1,37 @@
+import numpy as np
+
+
+class RunningMeanStd(object):
+    def __init__(self, epsilon=1e-4, shape=()):
+        """
+        calulates the running mean and std of a data stream
+        https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Parallel_algorithm
+
+        :param epsilon: (float) helps with arithmetic issues
+        :param shape: (tuple) the shape of the data stream's output
+        """
+        self.mean = np.zeros(shape, 'float64')
+        self.var = np.ones(shape, 'float64')
+        self.count = epsilon
+
+    def update(self, arr):
+        batch_mean = np.mean(arr, axis=0)
+        batch_var = np.var(arr, axis=0)
+        batch_count = arr.shape[0]
+        self.update_from_moments(batch_mean, batch_var, batch_count)
+
+    def update_from_moments(self, batch_mean, batch_var, batch_count):
+        delta = batch_mean - self.mean
+        tot_count = self.count + batch_count
+
+        new_mean = self.mean + delta * batch_count / tot_count
+        m_a = self.var * self.count
+        m_b = batch_var * batch_count
+        m_2 = m_a + m_b + np.square(delta) * self.count * batch_count / (self.count + batch_count)
+        new_var = m_2 / (self.count + batch_count)
+
+        new_count = batch_count + self.count
+
+        self.mean = new_mean
+        self.var = new_var
+        self.count = new_count
diff --git a/torchy_baselines/common/vec_env/__init__.py b/torchy_baselines/common/vec_env/__init__.py
new file mode 100644
index 0000000..3a58d12
--- /dev/null
+++ b/torchy_baselines/common/vec_env/__init__.py
@@ -0,0 +1,7 @@
+# flake8: noqa F401
+from torchy_baselines.common.vec_env.base_vec_env import AlreadySteppingError, NotSteppingError, VecEnv, VecEnvWrapper, \
+    CloudpickleWrapper
+from torchy_baselines.common.vec_env.dummy_vec_env import DummyVecEnv
+from torchy_baselines.common.vec_env.subproc_vec_env import SubprocVecEnv
+from torchy_baselines.common.vec_env.vec_frame_stack import VecFrameStack
+from torchy_baselines.common.vec_env.vec_normalize import VecNormalize
diff --git a/torchy_baselines/common/vec_env/base_vec_env.py b/torchy_baselines/common/vec_env/base_vec_env.py
new file mode 100644
index 0000000..26fec4b
--- /dev/null
+++ b/torchy_baselines/common/vec_env/base_vec_env.py
@@ -0,0 +1,301 @@
+from abc import ABCMeta, abstractmethod
+import inspect
+import pickle
+
+import cloudpickle
+
+
+class AlreadySteppingError(Exception):
+    """
+    Raised when an asynchronous step is running while
+    step_async() is called again.
+    """
+
+    def __init__(self):
+        msg = 'already running an async step'
+        Exception.__init__(self, msg)
+
+
+class NotSteppingError(Exception):
+    """
+    Raised when an asynchronous step is not running but
+    step_wait() is called.
+    """
+
+    def __init__(self):
+        msg = 'not running an async step'
+        Exception.__init__(self, msg)
+
+
+class VecEnv(object):
+    """
+    An abstract asynchronous, vectorized environment.
+
+    :param num_envs: (int) the number of environments
+    :param observation_space: (Gym Space) the observation space
+    :param action_space: (Gym Space) the action space
+    """
+    metadata = {
+        'render.modes': ['human', 'rgb_array']
+    }
+
+    __metaclass__ = ABCMeta
+
+    def __init__(self, num_envs, observation_space, action_space):
+        self.num_envs = num_envs
+        self.observation_space = observation_space
+        self.action_space = action_space
+
+    @abstractmethod
+    def reset(self):
+        """
+        Reset all the environments and return an array of
+        observations, or a tuple of observation arrays.
+
+        If step_async is still doing work, that work will
+        be cancelled and step_wait() should not be called
+        until step_async() is invoked again.
+
+        :return: ([int] or [float]) observation
+        """
+        pass
+
+    @abstractmethod
+    def step_async(self, actions):
+        """
+        Tell all the environments to start taking a step
+        with the given actions.
+        Call step_wait() to get the results of the step.
+
+        You should not call this if a step_async run is
+        already pending.
+        """
+        pass
+
+    @abstractmethod
+    def step_wait(self):
+        """
+        Wait for the step taken with step_async().
+
+        :return: ([int] or [float], [float], [bool], dict) observation, reward, done, information
+        """
+        pass
+
+    @abstractmethod
+    def close(self):
+        """
+        Clean up the environment's resources.
+        """
+        pass
+
+    @abstractmethod
+    def get_attr(self, attr_name, indices=None):
+        """
+        Return attribute from vectorized environment.
+
+        :param attr_name: (str) The name of the attribute whose value to return
+        :param indices: (list,int) Indices of envs to get attribute from
+        :return: (list) List of values of 'attr_name' in all environments
+        """
+        pass
+
+    @abstractmethod
+    def set_attr(self, attr_name, value, indices=None):
+        """
+        Set attribute inside vectorized environments.
+
+        :param attr_name: (str) The name of attribute to assign new value
+        :param value: (obj) Value to assign to `attr_name`
+        :param indices: (list,int) Indices of envs to assign value
+        :return: (NoneType)
+        """
+        pass
+
+    @abstractmethod
+    def env_method(self, method_name, *method_args, indices=None, **method_kwargs):
+        """
+        Call instance methods of vectorized environments.
+
+        :param method_name: (str) The name of the environment method to invoke.
+        :param indices: (list,int) Indices of envs whose method to call
+        :param method_args: (tuple) Any positional arguments to provide in the call
+        :param method_kwargs: (dict) Any keyword arguments to provide in the call
+        :return: (list) List of items returned by the environment's method call
+        """
+        pass
+
+    def step(self, actions):
+        """
+        Step the environments with the given action
+
+        :param actions: ([int] or [float]) the action
+        :return: ([int] or [float], [float], [bool], dict) observation, reward, done, information
+        """
+        self.step_async(actions)
+        return self.step_wait()
+
+    def get_images(self):
+        """
+        Return RGB images from each environment
+        """
+        raise NotImplementedError
+
+    def render(self, *args, **kwargs):
+        """
+        Gym environment rendering
+
+        :param mode: (str) the rendering type
+        """
+        raise NotImplementedError()
+
+    @property
+    def unwrapped(self):
+        if isinstance(self, VecEnvWrapper):
+            return self.venv.unwrapped
+        else:
+            return self
+
+    def getattr_depth_check(self, name, already_found):
+        """Check if an attribute reference is being hidden in a recursive call to __getattr__
+
+        :param name: (str) name of attribute to check for
+        :param already_found: (bool) whether this attribute has already been found in a wrapper
+        :return: (str or None) name of module whose attribute is being shadowed, if any.
+        """
+        if hasattr(self, name) and already_found:
+            return "{0}.{1}".format(type(self).__module__, type(self).__name__)
+        else:
+            return None
+
+    def _get_indices(self, indices):
+        """
+        Convert a flexibly-typed reference to environment indices to an implied list of indices.
+
+        :param indices: (None,int,Iterable) refers to indices of envs.
+        :return: (list) the implied list of indices.
+        """
+        if indices is None:
+            indices = range(self.num_envs)
+        elif isinstance(indices, int):
+            indices = [indices]
+        return indices
+
+
+class VecEnvWrapper(VecEnv):
+    """
+    Vectorized environment base class
+
+    :param venv: (VecEnv) the vectorized environment to wrap
+    :param observation_space: (Gym Space) the observation space (can be None to load from venv)
+    :param action_space: (Gym Space) the action space (can be None to load from venv)
+    """
+
+    def __init__(self, venv, observation_space=None, action_space=None):
+        self.venv = venv
+        VecEnv.__init__(self, num_envs=venv.num_envs, observation_space=observation_space or venv.observation_space,
+                        action_space=action_space or venv.action_space)
+        self.class_attributes = dict(inspect.getmembers(self.__class__))
+
+    def step_async(self, actions):
+        self.venv.step_async(actions)
+
+    @abstractmethod
+    def reset(self):
+        pass
+
+    @abstractmethod
+    def step_wait(self):
+        pass
+
+    def close(self):
+        return self.venv.close()
+
+    def render(self, *args, **kwargs):
+        return self.venv.render(*args, **kwargs)
+
+    def get_images(self):
+        return self.venv.get_images()
+
+    def get_attr(self, attr_name, indices=None):
+        return self.venv.get_attr(attr_name, indices)
+
+    def set_attr(self, attr_name, value, indices=None):
+        return self.venv.set_attr(attr_name, value, indices)
+
+    def env_method(self, method_name, *method_args, indices=None, **method_kwargs):
+        return self.venv.env_method(method_name, *method_args, indices=indices, **method_kwargs)
+
+    def __getattr__(self, name):
+        """Find attribute from wrapped venv(s) if this wrapper does not have it.
+        Useful for accessing attributes from venvs which are wrapped with multiple wrappers
+        which have unique attributes of interest.
+        """
+        blocked_class = self.getattr_depth_check(name, already_found=False)
+        if blocked_class is not None:
+            own_class = "{0}.{1}".format(type(self).__module__, type(self).__name__)
+            format_str = ("Error: Recursive attribute lookup for {0} from {1} is "
+                          "ambiguous and hides attribute from {2}")
+            raise AttributeError(format_str.format(name, own_class, blocked_class))
+
+        return self.getattr_recursive(name)
+
+    def _get_all_attributes(self):
+        """Get all (inherited) instance and class attributes
+
+        :return: (dict<str, object>) all_attributes
+        """
+        all_attributes = self.__dict__.copy()
+        all_attributes.update(self.class_attributes)
+        return all_attributes
+
+    def getattr_recursive(self, name):
+        """Recursively check wrappers to find attribute.
+
+        :param name (str) name of attribute to look for
+        :return: (object) attribute
+        """
+        all_attributes = self._get_all_attributes()
+        if name in all_attributes:  # attribute is present in this wrapper
+            attr = getattr(self, name)
+        elif hasattr(self.venv, 'getattr_recursive'):
+            # Attribute not present, child is wrapper. Call getattr_recursive rather than getattr
+            # to avoid a duplicate call to getattr_depth_check.
+            attr = self.venv.getattr_recursive(name)
+        else:  # attribute not present, child is an unwrapped VecEnv
+            attr = getattr(self.venv, name)
+
+        return attr
+
+    def getattr_depth_check(self, name, already_found):
+        """See base class.
+
+        :return: (str or None) name of module whose attribute is being shadowed, if any.
+        """
+        all_attributes = self._get_all_attributes()
+        if name in all_attributes and already_found:
+            # this venv's attribute is being hidden because of a higher venv.
+            shadowed_wrapper_class = "{0}.{1}".format(type(self).__module__, type(self).__name__)
+        elif name in all_attributes and not already_found:
+            # we have found the first reference to the attribute. Now check for duplicates.
+            shadowed_wrapper_class = self.venv.getattr_depth_check(name, True)
+        else:
+            # this wrapper does not have the attribute. Keep searching.
+            shadowed_wrapper_class = self.venv.getattr_depth_check(name, already_found)
+
+        return shadowed_wrapper_class
+
+
+class CloudpickleWrapper(object):
+    def __init__(self, var):
+        """
+        Uses cloudpickle to serialize contents (otherwise multiprocessing tries to use pickle)
+
+        :param var: (Any) the variable you wish to wrap for pickling with cloudpickle
+        """
+        self.var = var
+
+    def __getstate__(self):
+        return cloudpickle.dumps(self.var)
+
+    def __setstate__(self, obs):
+        self.var = pickle.loads(obs)
diff --git a/torchy_baselines/common/vec_env/dummy_vec_env.py b/torchy_baselines/common/vec_env/dummy_vec_env.py
new file mode 100644
index 0000000..a257b51
--- /dev/null
+++ b/torchy_baselines/common/vec_env/dummy_vec_env.py
@@ -0,0 +1,107 @@
+from collections import OrderedDict
+import numpy as np
+
+from torchy_baselines.common.vec_env import VecEnv
+from torchy_baselines.common.vec_env.util import copy_obs_dict, dict_to_obs, obs_space_info
+
+
+class DummyVecEnv(VecEnv):
+    """
+    Creates a simple vectorized wrapper for multiple environments, calling each environment in sequence on the current
+    Python process. This is useful for computationally simple environment such as ``cartpole-v1``, as the overhead of
+    multiprocess or multithread outweighs the environment computation time. This can also be used for RL methods that
+    require a vectorized environment, but that you want a single environments to train with.
+
+    :param env_fns: ([Gym Environment]) the list of environments to vectorize
+    """
+
+    def __init__(self, env_fns):
+        self.envs = [fn() for fn in env_fns]
+        env = self.envs[0]
+        VecEnv.__init__(self, len(env_fns), env.observation_space, env.action_space)
+        obs_space = env.observation_space
+        self.keys, shapes, dtypes = obs_space_info(obs_space)
+
+        self.buf_obs = OrderedDict([
+            (k, np.zeros((self.num_envs,) + tuple(shapes[k]), dtype=dtypes[k]))
+            for k in self.keys])
+        self.buf_dones = np.zeros((self.num_envs,), dtype=np.bool)
+        self.buf_rews = np.zeros((self.num_envs,), dtype=np.float32)
+        self.buf_infos = [{} for _ in range(self.num_envs)]
+        self.actions = None
+        self.metadata = env.metadata
+
+    def step_async(self, actions):
+        self.actions = actions
+
+    def step_wait(self):
+        for env_idx in range(self.num_envs):
+            obs, self.buf_rews[env_idx], self.buf_dones[env_idx], self.buf_infos[env_idx] =\
+                self.envs[env_idx].step(self.actions[env_idx])
+            if self.buf_dones[env_idx]:
+                # save final observation where user can get it, then reset
+                self.buf_infos[env_idx]['terminal_observation'] = obs
+                obs = self.envs[env_idx].reset()
+            self._save_obs(env_idx, obs)
+        return (self._obs_from_buf(), np.copy(self.buf_rews), np.copy(self.buf_dones),
+                self.buf_infos.copy())
+
+    def reset(self):
+        for env_idx in range(self.num_envs):
+            obs = self.envs[env_idx].reset()
+            self._save_obs(env_idx, obs)
+        return self._obs_from_buf()
+
+    def seed(self, seed, indices=None):
+        """
+        :param seed: (int or [int])
+        :param indices: ([int])
+        """
+        indices = self._get_indices(indices)
+        if not hasattr(seed, 'len'):
+            seed = [seed] * len(indices)
+        assert len(seed) == len(indices)
+        return [self.envs[i].seed(seed[i]) for i in indices]
+
+    def close(self):
+        for env in self.envs:
+            env.close()
+
+    def get_images(self):
+        return [env.render(mode='rgb_array') for env in self.envs]
+
+    def render(self, *args, **kwargs):
+        if self.num_envs == 1:
+            return self.envs[0].render(*args, **kwargs)
+        else:
+            return super().render(*args, **kwargs)
+
+    def _save_obs(self, env_idx, obs):
+        for key in self.keys:
+            if key is None:
+                self.buf_obs[key][env_idx] = obs
+            else:
+                self.buf_obs[key][env_idx] = obs[key]
+
+    def _obs_from_buf(self):
+        return dict_to_obs(self.observation_space, copy_obs_dict(self.buf_obs))
+
+    def get_attr(self, attr_name, indices=None):
+        """Return attribute from vectorized environment (see base class)."""
+        target_envs = self._get_target_envs(indices)
+        return [getattr(env_i, attr_name) for env_i in target_envs]
+
+    def set_attr(self, attr_name, value, indices=None):
+        """Set attribute inside vectorized environments (see base class)."""
+        target_envs = self._get_target_envs(indices)
+        for env_i in target_envs:
+            setattr(env_i, attr_name, value)
+
+    def env_method(self, method_name, *method_args, indices=None, **method_kwargs):
+        """Call instance methods of vectorized environments."""
+        target_envs = self._get_target_envs(indices)
+        return [getattr(env_i, method_name)(*method_args, **method_kwargs) for env_i in target_envs]
+
+    def _get_target_envs(self, indices):
+        indices = self._get_indices(indices)
+        return [self.envs[i] for i in indices]
diff --git a/torchy_baselines/common/vec_env/subproc_vec_env.py b/torchy_baselines/common/vec_env/subproc_vec_env.py
new file mode 100644
index 0000000..b746dac
--- /dev/null
+++ b/torchy_baselines/common/vec_env/subproc_vec_env.py
@@ -0,0 +1,232 @@
+import multiprocessing
+from collections import OrderedDict
+
+import gym
+import numpy as np
+
+from torchy_baselines.common.vec_env import VecEnv, CloudpickleWrapper
+
+
+def _worker(remote, parent_remote, env_fn_wrapper):
+    parent_remote.close()
+    env = env_fn_wrapper.var()
+    while True:
+        try:
+            cmd, data = remote.recv()
+            if cmd == 'step':
+                observation, reward, done, info = env.step(data)
+                if done:
+                    # save final observation where user can get it, then reset
+                    info['terminal_observation'] = observation
+                    observation = env.reset()
+                remote.send((observation, reward, done, info))
+            elif cmd == 'reset':
+                observation = env.reset()
+                remote.send(observation)
+            elif cmd == 'render':
+                remote.send(env.render(*data[0], **data[1]))
+            elif cmd == 'close':
+                remote.close()
+                break
+            elif cmd == 'get_spaces':
+                remote.send((env.observation_space, env.action_space))
+            elif cmd == 'env_method':
+                method = getattr(env, data[0])
+                remote.send(method(*data[1], **data[2]))
+            elif cmd == 'get_attr':
+                remote.send(getattr(env, data))
+            elif cmd == 'set_attr':
+                remote.send(setattr(env, data[0], data[1]))
+            else:
+                raise NotImplementedError
+        except EOFError:
+            break
+
+def tile_images(img_nhwc):
+    """
+    Tile N images into one big PxQ image
+    (P,Q) are chosen to be as close as possible, and if N
+    is square, then P=Q.
+
+    :param img_nhwc: (list) list or array of images, ndim=4 once turned into array. img nhwc
+        n = batch index, h = height, w = width, c = channel
+    :return: (numpy float) img_HWc, ndim=3
+    """
+    img_nhwc = np.asarray(img_nhwc)
+    n_images, height, width, n_channels = img_nhwc.shape
+    # new_height was named H before
+    new_height = int(np.ceil(np.sqrt(n_images)))
+    # new_width was named W before
+    new_width = int(np.ceil(float(n_images) / new_height))
+    img_nhwc = np.array(list(img_nhwc) + [img_nhwc[0] * 0 for _ in range(n_images, new_height * new_width)])
+    # img_HWhwc
+    out_image = img_nhwc.reshape(new_height, new_width, height, width, n_channels)
+    # img_HhWwc
+    out_image = out_image.transpose(0, 2, 1, 3, 4)
+    # img_Hh_Ww_c
+    out_image = out_image.reshape(new_height * height, new_width * width, n_channels)
+    return out_image
+
+
+
+class SubprocVecEnv(VecEnv):
+    """
+    Creates a multiprocess vectorized wrapper for multiple environments, distributing each environment to its own
+    process, allowing significant speed up when the environment is computationally complex.
+
+    For performance reasons, if your environment is not IO bound, the number of environments should not exceed the
+    number of logical cores on your CPU.
+
+    .. warning::
+
+        Only 'forkserver' and 'spawn' start methods are thread-safe,
+        which is important when TensorFlow sessions or other non thread-safe
+        libraries are used in the parent (see issue #217). However, compared to
+        'fork' they incur a small start-up cost and have restrictions on
+        global variables. With those methods, users must wrap the code in an
+        ``if __name__ == "__main__":`` block.
+        For more information, see the multiprocessing documentation.
+
+    :param env_fns: ([Gym Environment]) Environments to run in subprocesses
+    :param start_method: (str) method used to start the subprocesses.
+           Must be one of the methods returned by multiprocessing.get_all_start_methods().
+           Defaults to 'forkserver' on available platforms, and 'spawn' otherwise.
+    """
+
+    def __init__(self, env_fns, start_method=None):
+        self.waiting = False
+        self.closed = False
+        n_envs = len(env_fns)
+
+        if start_method is None:
+            # Fork is not a thread safe method (see issue #217)
+            # but is more user friendly (does not require to wrap the code in
+            # a `if __name__ == "__main__":`)
+            forkserver_available = 'forkserver' in multiprocessing.get_all_start_methods()
+            start_method = 'forkserver' if forkserver_available else 'spawn'
+        ctx = multiprocessing.get_context(start_method)
+
+        self.remotes, self.work_remotes = zip(*[ctx.Pipe() for _ in range(n_envs)])
+        self.processes = []
+        for work_remote, remote, env_fn in zip(self.work_remotes, self.remotes, env_fns):
+            args = (work_remote, remote, CloudpickleWrapper(env_fn))
+            # daemon=True: if the main process crashes, we should not cause things to hang
+            process = ctx.Process(target=_worker, args=args, daemon=True)
+            process.start()
+            self.processes.append(process)
+            work_remote.close()
+
+        self.remotes[0].send(('get_spaces', None))
+        observation_space, action_space = self.remotes[0].recv()
+        VecEnv.__init__(self, len(env_fns), observation_space, action_space)
+
+    def step_async(self, actions):
+        for remote, action in zip(self.remotes, actions):
+            remote.send(('step', action))
+        self.waiting = True
+
+    def step_wait(self):
+        results = [remote.recv() for remote in self.remotes]
+        self.waiting = False
+        obs, rews, dones, infos = zip(*results)
+        return _flatten_obs(obs, self.observation_space), np.stack(rews), np.stack(dones), infos
+
+    def reset(self):
+        for remote in self.remotes:
+            remote.send(('reset', None))
+        obs = [remote.recv() for remote in self.remotes]
+        return _flatten_obs(obs, self.observation_space)
+
+    def close(self):
+        if self.closed:
+            return
+        if self.waiting:
+            for remote in self.remotes:
+                remote.recv()
+        for remote in self.remotes:
+            remote.send(('close', None))
+        for process in self.processes:
+            process.join()
+        self.closed = True
+
+    def render(self, mode='human', *args, **kwargs):
+        for pipe in self.remotes:
+            # gather images from subprocesses
+            # `mode` will be taken into account later
+            pipe.send(('render', (args, {'mode': 'rgb_array', **kwargs})))
+        imgs = [pipe.recv() for pipe in self.remotes]
+        # Create a big image by tiling images from subprocesses
+        bigimg = tile_images(imgs)
+        if mode == 'human':
+            import cv2
+            cv2.imshow('vecenv', bigimg[:, :, ::-1])
+            cv2.waitKey(1)
+        elif mode == 'rgb_array':
+            return bigimg
+        else:
+            raise NotImplementedError
+
+    def get_images(self):
+        for pipe in self.remotes:
+            pipe.send(('render', {"mode": 'rgb_array'}))
+        imgs = [pipe.recv() for pipe in self.remotes]
+        return imgs
+
+    def get_attr(self, attr_name, indices=None):
+        """Return attribute from vectorized environment (see base class)."""
+        target_remotes = self._get_target_remotes(indices)
+        for remote in target_remotes:
+            remote.send(('get_attr', attr_name))
+        return [remote.recv() for remote in target_remotes]
+
+    def set_attr(self, attr_name, value, indices=None):
+        """Set attribute inside vectorized environments (see base class)."""
+        target_remotes = self._get_target_remotes(indices)
+        for remote in target_remotes:
+            remote.send(('set_attr', (attr_name, value)))
+        for remote in target_remotes:
+            remote.recv()
+
+    def env_method(self, method_name, *method_args, indices=None, **method_kwargs):
+        """Call instance methods of vectorized environments."""
+        target_remotes = self._get_target_remotes(indices)
+        for remote in target_remotes:
+            remote.send(('env_method', (method_name, method_args, method_kwargs)))
+        return [remote.recv() for remote in target_remotes]
+
+    def _get_target_remotes(self, indices):
+        """
+        Get the connection object needed to communicate with the wanted
+        envs that are in subprocesses.
+
+        :param indices: (None,int,Iterable) refers to indices of envs.
+        :return: ([multiprocessing.Connection]) Connection object to communicate between processes.
+        """
+        indices = self._get_indices(indices)
+        return [self.remotes[i] for i in indices]
+
+
+def _flatten_obs(obs, space):
+    """
+    Flatten observations, depending on the observation space.
+
+    :param obs: (list<X> or tuple<X> where X is dict<ndarray>, tuple<ndarray> or ndarray) observations.
+                A list or tuple of observations, one per environment.
+                Each environment observation may be a NumPy array, or a dict or tuple of NumPy arrays.
+    :return (OrderedDict<ndarray>, tuple<ndarray> or ndarray) flattened observations.
+            A flattened NumPy array or an OrderedDict or tuple of flattened numpy arrays.
+            Each NumPy array has the environment index as its first axis.
+    """
+    assert isinstance(obs, (list, tuple)), "expected list or tuple of observations per environment"
+    assert len(obs) > 0, "need observations from at least one environment"
+
+    if isinstance(space, gym.spaces.Dict):
+        assert isinstance(space.spaces, OrderedDict), "Dict space must have ordered subspaces"
+        assert isinstance(obs[0], dict), "non-dict observation for environment with Dict observation space"
+        return OrderedDict([(k, np.stack([o[k] for o in obs])) for k in space.spaces.keys()])
+    elif isinstance(space, gym.spaces.Tuple):
+        assert isinstance(obs[0], tuple), "non-tuple observation for environment with Tuple observation space"
+        obs_len = len(space.spaces)
+        return tuple((np.stack([o[i] for o in obs]) for i in range(obs_len)))
+    else:
+        return np.stack(obs)
diff --git a/torchy_baselines/common/vec_env/util.py b/torchy_baselines/common/vec_env/util.py
new file mode 100644
index 0000000..03ce286
--- /dev/null
+++ b/torchy_baselines/common/vec_env/util.py
@@ -0,0 +1,73 @@
+"""
+Helpers for dealing with vectorized environments.
+"""
+
+from collections import OrderedDict
+
+import gym
+import numpy as np
+
+
+def copy_obs_dict(obs):
+    """
+    Deep-copy a dict of numpy arrays.
+
+    :param obs: (OrderedDict<ndarray>): a dict of numpy arrays.
+    :return (OrderedDict<ndarray>) a dict of copied numpy arrays.
+    """
+    assert isinstance(obs, OrderedDict), "unexpected type for observations '{}'".format(type(obs))
+    return OrderedDict([(k, np.copy(v)) for k, v in obs.items()])
+
+
+def dict_to_obs(space, obs_dict):
+    """
+    Convert an internal representation raw_obs into the appropriate type
+    specified by space.
+
+    :param space: (gym.spaces.Space) an observation space.
+    :param obs_dict: (OrderedDict<ndarray>) a dict of numpy arrays.
+    :return (ndarray, tuple<ndarray> or dict<ndarray>): returns an observation
+            of the same type as space. If space is Dict, function is identity;
+            if space is Tuple, converts dict to Tuple; otherwise, space is
+            unstructured and returns the value raw_obs[None].
+    """
+    if isinstance(space, gym.spaces.Dict):
+        return obs_dict
+    elif isinstance(space, gym.spaces.Tuple):
+        assert len(obs_dict) == len(space.spaces), "size of observation does not match size of observation space"
+        return tuple((obs_dict[i] for i in range(len(space.spaces))))
+    else:
+        assert set(obs_dict.keys()) == {None}, "multiple observation keys for unstructured observation space"
+        return obs_dict[None]
+
+
+def obs_space_info(obs_space):
+    """
+    Get dict-structured information about a gym.Space.
+
+    Dict spaces are represented directly by their dict of subspaces.
+    Tuple spaces are converted into a dict with keys indexing into the tuple.
+    Unstructured spaces are represented by {None: obs_space}.
+
+    :param obs_space: (gym.spaces.Space) an observation space
+    :return (tuple) A tuple (keys, shapes, dtypes):
+        keys: a list of dict keys.
+        shapes: a dict mapping keys to shapes.
+        dtypes: a dict mapping keys to dtypes.
+    """
+    if isinstance(obs_space, gym.spaces.Dict):
+        assert isinstance(obs_space.spaces, OrderedDict), "Dict space must have ordered subspaces"
+        subspaces = obs_space.spaces
+    elif isinstance(obs_space, gym.spaces.Tuple):
+        subspaces = {i: space for i, space in enumerate(obs_space.spaces)}
+    else:
+        assert not hasattr(obs_space, 'spaces'), "Unsupported structured space '{}'".format(type(obs_space))
+        subspaces = {None: obs_space}
+    keys = []
+    shapes = {}
+    dtypes = {}
+    for key, box in subspaces.items():
+        keys.append(key)
+        shapes[key] = box.shape
+        dtypes[key] = box.dtype
+    return keys, shapes, dtypes
diff --git a/torchy_baselines/common/vec_env/vec_frame_stack.py b/torchy_baselines/common/vec_env/vec_frame_stack.py
new file mode 100644
index 0000000..2610f42
--- /dev/null
+++ b/torchy_baselines/common/vec_env/vec_frame_stack.py
@@ -0,0 +1,55 @@
+import warnings
+
+import numpy as np
+from gym import spaces
+
+from torchy_baselines.common.vec_env import VecEnvWrapper
+
+
+class VecFrameStack(VecEnvWrapper):
+    """
+    Frame stacking wrapper for vectorized environment
+
+    :param venv: (VecEnv) the vectorized environment to wrap
+    :param n_stack: (int) Number of frames to stack
+    """
+
+    def __init__(self, venv, n_stack):
+        self.venv = venv
+        self.n_stack = n_stack
+        wrapped_obs_space = venv.observation_space
+        low = np.repeat(wrapped_obs_space.low, self.n_stack, axis=-1)
+        high = np.repeat(wrapped_obs_space.high, self.n_stack, axis=-1)
+        self.stackedobs = np.zeros((venv.num_envs,) + low.shape, low.dtype)
+        observation_space = spaces.Box(low=low, high=high, dtype=venv.observation_space.dtype)
+        VecEnvWrapper.__init__(self, venv, observation_space=observation_space)
+
+    def step_wait(self):
+        observations, rewards, dones, infos = self.venv.step_wait()
+        last_ax_size = observations.shape[-1]
+        self.stackedobs = np.roll(self.stackedobs, shift=-last_ax_size, axis=-1)
+        for i, done in enumerate(dones):
+            if done:
+                if 'terminal_observation' in infos[i]:
+                    old_terminal = infos[i]['terminal_observation']
+                    new_terminal = np.concatenate(
+                        (self.stackedobs[i, ..., :-last_ax_size], old_terminal), axis=-1)
+                    infos[i]['terminal_observation'] = new_terminal
+                else:
+                    warnings.warn(
+                        "VecFrameStack wrapping a VecEnv without terminal_observation info")
+                self.stackedobs[i] = 0
+        self.stackedobs[..., -observations.shape[-1]:] = observations
+        return self.stackedobs, rewards, dones, infos
+
+    def reset(self):
+        """
+        Reset all environments
+        """
+        obs = self.venv.reset()
+        self.stackedobs[...] = 0
+        self.stackedobs[..., -obs.shape[-1]:] = obs
+        return self.stackedobs
+
+    def close(self):
+        self.venv.close()
diff --git a/torchy_baselines/common/vec_env/vec_normalize.py b/torchy_baselines/common/vec_env/vec_normalize.py
new file mode 100644
index 0000000..6f2b2b3
--- /dev/null
+++ b/torchy_baselines/common/vec_env/vec_normalize.py
@@ -0,0 +1,105 @@
+import pickle
+
+import numpy as np
+
+from torchy_baselines.common.vec_env import VecEnvWrapper
+from torchy_baselines.common.running_mean_std import RunningMeanStd
+
+
+class VecNormalize(VecEnvWrapper):
+    """
+    A moving average, normalizing wrapper for vectorized environment.
+    has support for saving/loading moving average,
+
+    :param venv: (VecEnv) the vectorized environment to wrap
+    :param training: (bool) Whether to update or not the moving average
+    :param norm_obs: (bool) Whether to normalize observation or not (default: True)
+    :param norm_reward: (bool) Whether to normalize rewards or not (default: True)
+    :param clip_obs: (float) Max absolute value for observation
+    :param clip_reward: (float) Max value absolute for discounted reward
+    :param gamma: (float) discount factor
+    :param epsilon: (float) To avoid division by zero
+    """
+
+    def __init__(self, venv, training=True, norm_obs=True, norm_reward=True,
+                 clip_obs=10., clip_reward=10., gamma=0.99, epsilon=1e-8):
+        VecEnvWrapper.__init__(self, venv)
+        self.obs_rms = RunningMeanStd(shape=self.observation_space.shape)
+        self.ret_rms = RunningMeanStd(shape=())
+        self.clip_obs = clip_obs
+        self.clip_reward = clip_reward
+        # Returns: discounted rewards
+        self.ret = np.zeros(self.num_envs)
+        self.gamma = gamma
+        self.epsilon = epsilon
+        self.training = training
+        self.norm_obs = norm_obs
+        self.norm_reward = norm_reward
+        self.old_obs = np.array([])
+
+    def step_wait(self):
+        """
+        Apply sequence of actions to sequence of environments
+        actions -> (observations, rewards, news)
+
+        where 'news' is a boolean vector indicating whether each element is new.
+        """
+        obs, rews, news, infos = self.venv.step_wait()
+        self.ret = self.ret * self.gamma + rews
+        self.old_obs = obs
+        obs = self._normalize_observation(obs)
+        if self.norm_reward:
+            if self.training:
+                self.ret_rms.update(self.ret)
+            rews = np.clip(rews / np.sqrt(self.ret_rms.var + self.epsilon), -self.clip_reward, self.clip_reward)
+        self.ret[news] = 0
+        return obs, rews, news, infos
+
+    def _normalize_observation(self, obs):
+        """
+        :param obs: (numpy tensor)
+        """
+        if self.norm_obs:
+            if self.training:
+                self.obs_rms.update(obs)
+            obs = np.clip((obs - self.obs_rms.mean) / np.sqrt(self.obs_rms.var + self.epsilon), -self.clip_obs,
+                          self.clip_obs)
+            return obs
+        else:
+            return obs
+
+    def get_original_obs(self):
+        """
+        returns the unnormalized observation
+
+        :return: (numpy float)
+        """
+        return self.old_obs
+
+    def reset(self):
+        """
+        Reset all environments
+        """
+        obs = self.venv.reset()
+        if len(np.array(obs).shape) == 1:  # for when num_cpu is 1
+            self.old_obs = [obs]
+        else:
+            self.old_obs = obs
+        self.ret = np.zeros(self.num_envs)
+        return self._normalize_observation(obs)
+
+    def save_running_average(self, path):
+        """
+        :param path: (str) path to log dir
+        """
+        for rms, name in zip([self.obs_rms, self.ret_rms], ['obs_rms', 'ret_rms']):
+            with open("{}/{}.pkl".format(path, name), 'wb') as file_handler:
+                pickle.dump(rms, file_handler)
+
+    def load_running_average(self, path):
+        """
+        :param path: (str) path to log dir
+        """
+        for name in ['obs_rms', 'ret_rms']:
+            with open("{}/{}.pkl".format(path, name), 'rb') as file_handler:
+                setattr(self, name, pickle.load(file_handler))