diff --git a/examples/simple_example_3.py b/examples/simple_example_3.py
index 1661ef65a9a33f3b44a098caaf83317919722398..e015b3c88cf05a8d047f15dfaf88e8a2fd9ce789 100644
--- a/examples/simple_example_3.py
+++ b/examples/simple_example_3.py
@@ -2,7 +2,7 @@ import random
 
 import numpy as np
 
-from flatland.envs.generators import random_rail_generator
+from flatland.envs.generators import random_rail_generator, complex_rail_generator
 from flatland.envs.observations import TreeObsForRailEnv
 from flatland.envs.rail_env import RailEnv
 from flatland.utils.rendertools import RenderTool
diff --git a/flatland/envs/agent_utils.py b/flatland/envs/agent_utils.py
index 8e9ffb99d06176416dfbe2b65bcca09723b1a56c..aa46aecd4b69b6a13b11b63223123b16dd69e3ac 100644
--- a/flatland/envs/agent_utils.py
+++ b/flatland/envs/agent_utils.py
@@ -28,19 +28,34 @@ class EnvAgentStatic(object):
     position = attrib()
     direction = attrib()
     target = attrib()
-    moving = attrib()
-
-    def __init__(self, position, direction, target, moving=False):
+    moving = attrib(default=False)
+    # speed_data: speed is added to position_fraction on each moving step, until position_fraction>=1.0,
+    # after which 'transition_action_on_cellexit' is executed (equivalent to executing that action in the previous
+    # cell if speed=1, as default)
+    speed_data = attrib(default=dict({'position_fraction': 0.0, 'speed': 1.0, 'transition_action_on_cellexit': 0}))
+
+    def __init__(self,
+                 position,
+                 direction,
+                 target,
+                 moving=False,
+                 speed_data={'position_fraction': 0.0, 'speed': 1.0, 'transition_action_on_cellexit': 0}):
         self.position = position
         self.direction = direction
         self.target = target
         self.moving = moving
+        self.speed_data = speed_data
 
     @classmethod
-    def from_lists(cls, positions, directions, targets):
+    def from_lists(cls, positions, directions, targets, speeds=None):
         """ Create a list of EnvAgentStatics from lists of positions, directions and targets
         """
-        return list(starmap(EnvAgentStatic, zip(positions, directions, targets, [False] * len(positions))))
+        speed_datas = []
+        for i in range(len(positions)):
+            speed_datas.append({'position_fraction': 0.0,
+                                'speed': speeds[i] if speeds is not None else 1.0,
+                                'transition_action_on_cellexit': 0})
+        return list(starmap(EnvAgentStatic, zip(positions, directions, targets, [False] * len(positions), speed_datas)))
 
     def to_list(self):
 
@@ -54,7 +69,7 @@ class EnvAgentStatic(object):
         if type(lTarget) is np.ndarray:
             lTarget = lTarget.tolist()
 
-        return [lPos, int(self.direction), lTarget, int(self.moving)]
+        return [lPos, int(self.direction), lTarget, int(self.moving), self.speed_data]
 
 
 @attrs
@@ -78,7 +93,7 @@ class EnvAgent(EnvAgentStatic):
     def to_list(self):
         return [
             self.position, self.direction, self.target, self.handle,
-            self.old_direction, self.old_position, self.moving]
+            self.old_direction, self.old_position, self.moving, self.speed_data]
 
     @classmethod
     def from_static(cls, oStatic):
diff --git a/flatland/envs/generators.py b/flatland/envs/generators.py
index f644bc120d4b514f1c54e0330cfc8dc4654a4f4e..ca14667424d2c93d1466e3b7e96c2e5c1fbd41e5 100644
--- a/flatland/envs/generators.py
+++ b/flatland/envs/generators.py
@@ -18,7 +18,7 @@ def empty_rail_generator():
         rail_array = grid_map.grid
         rail_array.fill(0)
 
-        return grid_map, [], [], []
+        return grid_map, [], [], [], []
 
     return generator
 
@@ -75,8 +75,9 @@ def complex_rail_generator(nr_start_goal=1, nr_extra=100, min_dist=20, max_dist=
         while nr_created < nr_start_goal and created_sanity < sanity_max:
             all_ok = False
             for _ in range(sanity_max):
-                start = (np.random.randint(0, width), np.random.randint(0, height))
-                goal = (np.random.randint(0, height), np.random.randint(0, height))
+                start = (np.random.randint(0, height), np.random.randint(0, width))
+                goal = (np.random.randint(0, height), np.random.randint(0, width))
+
                 # check to make sure start,goal pos is empty?
                 if rail_array[goal] != 0 or rail_array[start] != 0:
                     continue
@@ -121,8 +122,8 @@ def complex_rail_generator(nr_start_goal=1, nr_extra=100, min_dist=20, max_dist=
         while nr_created < nr_extra and created_sanity < sanity_max:
             all_ok = False
             for _ in range(sanity_max):
-                start = (np.random.randint(0, width), np.random.randint(0, height))
-                goal = (np.random.randint(0, height), np.random.randint(0, height))
+                start = (np.random.randint(0, height), np.random.randint(0, width))
+                goal = (np.random.randint(0, height), np.random.randint(0, width))
                 # check to make sure start,goal pos are not empty
                 if rail_array[goal] == 0 or rail_array[start] == 0:
                     continue
@@ -139,7 +140,7 @@ def complex_rail_generator(nr_start_goal=1, nr_extra=100, min_dist=20, max_dist=
         agents_target = [sg[1] for sg in start_goal[:num_agents]]
         agents_direction = start_dir[:num_agents]
 
-        return grid_map, agents_position, agents_direction, agents_target
+        return grid_map, agents_position, agents_direction, agents_target, [1.0]*len(agents_position)
 
     return generator
 
@@ -183,7 +184,7 @@ def rail_from_manual_specifications_generator(rail_spec):
             rail,
             num_agents)
 
-        return rail, agents_position, agents_direction, agents_target
+        return rail, agents_position, agents_direction, agents_target, [1.0]*len(agents_position)
 
     return generator
 
@@ -209,7 +210,7 @@ def rail_from_GridTransitionMap_generator(rail_map):
             rail_map,
             num_agents)
 
-        return rail_map, agents_position, agents_direction, agents_target
+        return rail_map, agents_position, agents_direction, agents_target, [1.0]*len(agents_position)
 
     return generator
 
@@ -482,6 +483,6 @@ def random_rail_generator(cell_type_relative_proportion=[1.0] * 11):
             return_rail,
             num_agents)
 
-        return return_rail, agents_position, agents_direction, agents_target
+        return return_rail, agents_position, agents_direction, agents_target, [1.0]*len(agents_position)
 
     return generator
diff --git a/flatland/envs/rail_env.py b/flatland/envs/rail_env.py
index c22e1c5120b54a170f9c59bb54c7666ca910f086..8cf6d52f383ec8f4e271eb0765d32bc0c763307a 100644
--- a/flatland/envs/rail_env.py
+++ b/flatland/envs/rail_env.py
@@ -73,7 +73,7 @@ class RailEnv(Environment):
                 random_rail_generator : generate a random rail of given size
                 rail_from_GridTransitionMap_generator(rail_map) : generate a rail from
                                         a GridTransitionMap object
-                rail_from_manual_specifications_generator(rail_spec) : generate a rail from
+                rail_from_manual_sp ecifications_generator(rail_spec) : generate a rail from
                                         a rail specifications array
                 TODO: generate_rail_from_saved_list or from list of ndarray bitmaps ---
         width : int
@@ -101,7 +101,6 @@ class RailEnv(Environment):
         self.action_space = [1]
         self.observation_space = self.obs_builder.observation_space  # updated on resets?
 
-        self.actions = [0] * number_of_agents
         self.rewards = [0] * number_of_agents
         self.done = False
 
@@ -152,7 +151,7 @@ class RailEnv(Environment):
             self.rail = tRailAgents[0]
 
         if replace_agents:
-            self.agents_static = EnvAgentStatic.from_lists(*tRailAgents[1:4])
+            self.agents_static = EnvAgentStatic.from_lists(*tRailAgents[1:5])
 
         self.restart_agents()
 
@@ -193,28 +192,26 @@ class RailEnv(Environment):
         for iAgent in range(self.get_num_agents()):
             agent = self.agents[iAgent]
 
-            if iAgent not in action_dict:  # no action has been supplied for this agent
-                if agent.moving:
-                    # Keep moving
-                    # Change MOVE_FORWARD to DO_NOTHING
-                    action_dict[iAgent] = RailEnvActions.DO_NOTHING
-                else:
-                    action_dict[iAgent] = RailEnvActions.DO_NOTHING
-
             if self.dones[iAgent]:  # this agent has already completed...
                 continue
-            action = action_dict[iAgent]
 
-            if action < 0 or action > len(RailEnvActions):
-                print('ERROR: illegal action=', action,
-                      'for agent with index=', iAgent)
-                return
+            if iAgent not in action_dict:  # no action has been supplied for this agent
+                action_dict[iAgent] = RailEnvActions.DO_NOTHING
+
+            if action_dict[iAgent] < 0 or action_dict[iAgent] > len(RailEnvActions):
+                print('ERROR: illegal action=', action_dict[iAgent],
+                      'for agent with index=', iAgent,
+                      '"DO NOTHING" will be executed instead')
+                action_dict[iAgent] = RailEnvActions.DO_NOTHING
+
+            action = action_dict[iAgent]
 
             if action == RailEnvActions.DO_NOTHING and agent.moving:
                 # Keep moving
                 action = RailEnvActions.MOVE_FORWARD
 
-            if action == RailEnvActions.STOP_MOVING and agent.moving:
+            if action == RailEnvActions.STOP_MOVING and agent.moving and agent.speed_data['position_fraction'] < 0.01:
+                # Only allow halting an agent on entering new cells.
                 agent.moving = False
                 self.rewards_dict[iAgent] += stop_penalty
 
@@ -223,47 +220,78 @@ class RailEnv(Environment):
                 agent.moving = True
                 self.rewards_dict[iAgent] += start_penalty
 
-            if action != RailEnvActions.DO_NOTHING and action != RailEnvActions.STOP_MOVING:
-                cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
-                    self._check_action_on_agent(action, agent)
-                if all([new_cell_isValid, transition_isValid, cell_isFree]):
-                    agent.old_direction = agent.direction
-                    agent.old_position = agent.position
-                    agent.position = new_position
-                    agent.direction = new_direction
-                else:
-                    # Logic: if the chosen action is invalid,
-                    # and it was LEFT or RIGHT, and the agent was moving, then keep moving FORWARD.
-                    if (action == RailEnvActions.MOVE_LEFT or action == RailEnvActions.MOVE_RIGHT) and agent.moving:
-                        cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
-                            self._check_action_on_agent(RailEnvActions.MOVE_FORWARD, agent)
-
-                        if all([new_cell_isValid, transition_isValid, cell_isFree]):
-                            agent.old_direction = agent.direction
-                            agent.old_position = agent.position
-                            agent.position = new_position
-                            agent.direction = new_direction
+            # Now perform a movement.
+            # If the agent is in an initial position within a new cell (agent.speed_data['position_fraction']<eps)
+            #   store the desired action in `transition_action_on_cellexit' (only if the desired transition is
+            #   allowed! otherwise DO_NOTHING!)
+            # Then in any case (if agent.moving) and the `transition_action_on_cellexit' is valid, increment the
+            #   position_fraction by the speed of the agent   (regardless of action taken, as long as no
+            #   STOP_MOVING, but that makes agent.moving=False)
+            # If the new position fraction is >= 1, reset to 0, and perform the stored
+            #   transition_action_on_cellexit
+
+            # If the agent can make an action
+            action_selected = False
+            if agent.speed_data['position_fraction'] < 0.01:
+                if action != RailEnvActions.DO_NOTHING and action != RailEnvActions.STOP_MOVING:
+                    cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
+                        self._check_action_on_agent(action, agent)
+
+                    if all([new_cell_isValid, transition_isValid, cell_isFree]):
+                        agent.speed_data['transition_action_on_cellexit'] = action
+                        action_selected = True
+
+                    else:
+                        # But, if the chosen invalid action was LEFT/RIGHT, and the agent is moving,
+                        # try to keep moving forward!
+                        if (action == RailEnvActions.MOVE_LEFT or action == RailEnvActions.MOVE_RIGHT) and agent.moving:
+                            cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
+                                self._check_action_on_agent(RailEnvActions.MOVE_FORWARD, agent)
+
+                            if all([new_cell_isValid, transition_isValid, cell_isFree]):
+                                agent.speed_data['transition_action_on_cellexit'] = RailEnvActions.MOVE_FORWARD
+                                action_selected = True
+
+                            else:
+                                # TODO: an invalid action was chosen after entering the cell. The agent cannot move.
+                                self.rewards_dict[iAgent] += invalid_action_penalty
+                                agent.moving = False
+                                self.rewards_dict[iAgent] += stop_penalty
+                                continue
                         else:
-                            # the action was not valid, add penalty
+                            # TODO: an invalid action was chosen after entering the cell. The agent cannot move.
                             self.rewards_dict[iAgent] += invalid_action_penalty
+                            agent.moving = False
+                            self.rewards_dict[iAgent] += stop_penalty
+                            continue
 
-                    else:
-                        # the action was not valid, add penalty
-                        self.rewards_dict[iAgent] += invalid_action_penalty
+            if agent.moving and (action_selected or agent.speed_data['position_fraction'] >= 0.01):
+                agent.speed_data['position_fraction'] += agent.speed_data['speed']
+
+            if agent.speed_data['position_fraction'] >= 1.0:
+                agent.speed_data['position_fraction'] = 0.0
+
+                # Perform stored action to transition to the next cell
+
+                # Now 'transition_action_on_cellexit' will be guaranteed to be valid; it was checked on entering
+                # the cell
+                cell_isFree, new_cell_isValid, new_direction, new_position, transition_isValid = \
+                    self._check_action_on_agent(agent.speed_data['transition_action_on_cellexit'], agent)
+                agent.old_direction = agent.direction
+                agent.old_position = agent.position
+                agent.position = new_position
+                agent.direction = new_direction
 
             if np.equal(agent.position, agent.target).all():
                 self.dones[iAgent] = True
             else:
-                self.rewards_dict[iAgent] += step_penalty
+                self.rewards_dict[iAgent] += step_penalty * agent.speed_data['speed']
 
         # Check for end of episode + add global reward to all rewards!
         if np.all([np.array_equal(agent2.position, agent2.target) for agent2 in self.agents]):
             self.dones["__all__"] = True
             self.rewards_dict = [0 * r + global_reward for r in self.rewards_dict]
 
-        # Reset the step actions (in case some agent doesn't 'register_action'
-        # on the next step)
-        self.actions = [0] * self.get_num_agents()
         return self._get_observations(), self.rewards_dict, self.dones, {}
 
     def _check_action_on_agent(self, action, agent):
@@ -271,6 +299,7 @@ class RailEnv(Environment):
         # cell used to check for invalid actions
         new_direction, transition_isValid = self.check_action(agent, action)
         new_position = get_new_position(agent.position, new_direction)
+
         # Is it a legal move?
         # 1) transition allows the new_direction in the cell,
         # 2) the new cell is not empty (case 0),
@@ -281,11 +310,13 @@ class RailEnv(Environment):
                 np.clip(new_position, [0, 0], [self.height - 1, self.width - 1]))
             and  # check the new position has some transitions (ie is not an empty cell)
             self.rail.get_transitions(new_position) > 0)
+
         # If transition validity hasn't been checked yet.
         if transition_isValid is None:
             transition_isValid = self.rail.get_transition(
                 (*agent.position, agent.direction),
                 new_direction)
+
         # Check the new position is not the same as any of the existing agent positions
         # (including itself, for simplicity, since it is moving)
         cell_isFree = not np.any(
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/tests/test_environments.py b/tests/test_environments.py
index 11f0acba2fd54df63c62047f8559897e7d222e72..aa24467dd1d548a2b68a408f300089ee8135c639 100644
--- a/tests/test_environments.py
+++ b/tests/test_environments.py
@@ -3,7 +3,7 @@
 import numpy as np
 
 from flatland.core.transition_map import GridTransitionMap
-from flatland.core.transitions import Grid4Transitions
+from flatland.core.transitions import Grid4Transitions, RailEnvTransitions
 from flatland.envs.agent_utils import EnvAgent
 from flatland.envs.generators import complex_rail_generator
 from flatland.envs.generators import rail_from_GridTransitionMap_generator
@@ -53,7 +53,7 @@ def test_rail_environment_single_agent():
     # | |  |
     # \_/\_/
 
-    transitions = Grid4Transitions([])
+    transitions = RailEnvTransitions()
     vertical_line = cells[1]
     south_symmetrical_switch = cells[6]
     north_symmetrical_switch = transitions.rotate_transition(south_symmetrical_switch, 180)
@@ -107,6 +107,7 @@ def test_rail_environment_single_agent():
             if prev_pos != pos:
                 valid_active_actions_done += 1
 
+
         # After 6 movements on this railway network, the train should be back
         # to its original height on the map.
         assert (initial_pos[0] == agent.position[0])
@@ -121,9 +122,9 @@ def test_rail_environment_single_agent():
                 action = np.random.randint(4)
 
                 _, _, dones, _ = rail_env.step({0: action})
-
                 done = dones['__all__']
 
+test_rail_environment_single_agent()
 
 def test_dead_end():
     transitions = Grid4Transitions([])