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Initial OpenEnv traffic signal environment
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import random
from dataclasses import dataclass, field
from typing import Dict, Iterable, Optional, Tuple
from models import EmergencyVehicle, LANES, VEHICLE_TYPES, LaneQueues, TrafficAction, TrafficState
from tasks import get_task
LANE_GROUPS = {
TrafficAction.NS_GREEN: ("N", "S"),
TrafficAction.EW_GREEN: ("E", "W"),
TrafficAction.LEFT_PRIORITY: ("N", "E"),
}
VEHICLE_CLEARANCE_UNITS = {
"cars": 1.0,
"bikes": 0.45,
"autos": 0.75,
"buses": 2.2,
"trucks": 2.5,
}
@dataclass
class TrafficMetrics:
total_vehicles_cleared: int = 0
total_wait_observations: float = 0.0
wait_samples: int = 0
max_queue_length: int = 0
emergency_seen: int = 0
emergency_cleared_fast: int = 0
unsafe_switches: int = 0
full_clearances: int = 0
@dataclass
class StepDiagnostics:
vehicles_cleared: int = 0
unsafe_switch_penalty: int = 0
emergency_clear_bonus: int = 0
raw_reward: float = 0.0
normalized_reward: float = 0.0
invalid_action: bool = False
notes: list = field(default_factory=list)
class IndianTrafficEnv:
"""Deterministic mixed-traffic signal environment for one Indian urban intersection.
The class is intentionally network-ready: lane state and flow calculations are kept
per-lane, so a future MultiIntersectionEnv can compose several instances.
"""
def __init__(self, task_id: str = "single_intersection"):
self.task_id = task_id
self.task = get_task(task_id)
self.rng = random.Random()
self.seed_value = 42
self.tick = 0
self.current_phase = TrafficAction.ALL_RED
self.time_since_switch = 0
self.queues: Dict[str, Dict[str, int]] = {}
self.waiting_time: Dict[str, float] = {}
self.last_inflow: Dict[str, Dict[str, int]] = {}
self.pedestrian_count = 0
self.pedestrian_wait_time = 0.0
self.emergency = EmergencyVehicle(present=False)
self.rain_level = float(self.task.constraints["rain_level"])
self.driver_aggression = 0.4
self.random_blockage_probability = 0.02
self.peak_hour_multiplier = float(self.task.constraints["initial_peak_multiplier"])
self.metrics = TrafficMetrics()
self.done = False
self.reset(self.seed_value, task_id)
def reset(self, seed: Optional[int] = None, task_id: Optional[str] = None) -> TrafficState:
if task_id is not None:
self.task_id = task_id
self.task = get_task(task_id)
self.seed_value = 42 if seed is None else int(seed)
self.rng = random.Random(self.seed_value)
self.tick = 0
self.current_phase = TrafficAction.ALL_RED
self.time_since_switch = 0
self.rain_level = float(self.task.constraints["rain_level"])
self.driver_aggression = self.rng.uniform(0.22, 0.72)
self.random_blockage_probability = self.rng.uniform(0.01, 0.05)
self.peak_hour_multiplier = float(self.task.constraints["initial_peak_multiplier"])
self.queues = {lane: self._sample_initial_lane(lane) for lane in LANES}
self.waiting_time = {lane: 0.0 for lane in LANES}
self.last_inflow = {lane: {vehicle: 0 for vehicle in VEHICLE_TYPES} for lane in LANES}
self.pedestrian_count = self.rng.randint(2, 14)
self.pedestrian_wait_time = 0.0
self.emergency = EmergencyVehicle(present=False)
self.metrics = TrafficMetrics()
self.done = False
return self.get_state()
def step(self, action: TrafficAction) -> Tuple[TrafficState, float, bool, Dict[str, object]]:
if self.done:
return self.get_state(), 0.0, True, {"message": "Episode already complete."}
diagnostics = StepDiagnostics()
try:
action = TrafficAction(action)
except ValueError:
action = TrafficAction.ALL_RED
diagnostics.invalid_action = True
diagnostics.notes.append("Invalid action converted to ALL_RED.")
effective_action = self._apply_action_constraints(action, diagnostics)
self._maybe_switch_phase(effective_action)
self.last_inflow = self._generate_inflow()
self._add_inflow(self.last_inflow)
self._maybe_spawn_emergency()
diagnostics.vehicles_cleared = self._clear_traffic(effective_action)
emergency_cleared = self._update_emergency(effective_action)
diagnostics.emergency_clear_bonus = 1 if emergency_cleared else 0
self._update_pedestrians(effective_action)
self._update_waiting_times()
queue_length = self._total_queue_length()
total_wait = sum(self.waiting_time.values())
self.metrics.total_vehicles_cleared += diagnostics.vehicles_cleared
self.metrics.total_wait_observations += total_wait
self.metrics.wait_samples += 1
self.metrics.max_queue_length = max(self.metrics.max_queue_length, queue_length)
if queue_length == 0:
self.metrics.full_clearances += 1
reward = self._calculate_reward(
vehicles_cleared=diagnostics.vehicles_cleared,
total_waiting_time=total_wait,
queue_length=queue_length,
pedestrian_wait_time=self.pedestrian_wait_time,
unsafe_switch_penalty=diagnostics.unsafe_switch_penalty,
emergency_clear_bonus=diagnostics.emergency_clear_bonus,
diagnostics=diagnostics,
)
self.tick += 1
self.time_since_switch += 1
self.done = self._is_done(queue_length)
return self.get_state(), reward, self.done, self._info(diagnostics)
def get_state(self) -> TrafficState:
return TrafficState(
tick=self.tick,
lane_queues={lane: LaneQueues(**self.queues[lane]) for lane in LANES},
lane_waiting_time={lane: round(self.waiting_time[lane], 3) for lane in LANES},
current_signal_phase=self.current_phase,
time_since_last_phase_switch=self.time_since_switch,
pedestrian_count=self.pedestrian_count,
pedestrian_wait_time=round(self.pedestrian_wait_time, 3),
emergency_vehicle=self.emergency,
rain_level=round(self.rain_level, 3),
random_traffic_inflow={lane: LaneQueues(**self.last_inflow[lane]) for lane in LANES},
)
def _sample_initial_lane(self, lane: str) -> Dict[str, int]:
arterial_bonus = 3 if lane in ("N", "S") else 1
return {
"cars": self.rng.randint(3 + arterial_bonus, 8 + arterial_bonus),
"bikes": self.rng.randint(6 + arterial_bonus, 14 + arterial_bonus),
"autos": self.rng.randint(2, 6),
"buses": self.rng.randint(0, 2),
"trucks": self.rng.randint(0, 2),
}
def _generate_inflow(self) -> Dict[str, Dict[str, int]]:
inflow = {}
rain_slowdown = 1.0 + self.rain_level * 0.25
for lane in LANES:
arterial = 1.25 if lane in ("N", "S") else 0.95
base = self.peak_hour_multiplier * arterial * rain_slowdown
inflow[lane] = {
"cars": self._bounded_arrivals(base, 2),
"bikes": self._bounded_arrivals(base * 1.8, 4),
"autos": self._bounded_arrivals(base * 0.85, 2),
"buses": 1 if self.rng.random() < 0.08 * base else 0,
"trucks": 1 if self.rng.random() < 0.06 * base else 0,
}
if self.tick % 40 == 0 and self.tick > 0:
self.peak_hour_multiplier = max(0.8, self.peak_hour_multiplier * 0.94)
return inflow
def _bounded_arrivals(self, intensity: float, cap: int) -> int:
arrivals = int(intensity)
fractional = intensity - arrivals
if self.rng.random() < fractional:
arrivals += 1
if self.rng.random() < 0.12 * self.peak_hour_multiplier:
arrivals += 1
return max(0, min(cap, arrivals))
def _add_inflow(self, inflow: Dict[str, Dict[str, int]]) -> None:
for lane in LANES:
for vehicle in VEHICLE_TYPES:
self.queues[lane][vehicle] += inflow[lane][vehicle]
def _apply_action_constraints(self, action: TrafficAction, diagnostics: StepDiagnostics) -> TrafficAction:
min_green = int(self.task.constraints["min_green_time"])
switching = action != self.current_phase and action not in (TrafficAction.EXTEND_GREEN, TrafficAction.EMERGENCY_OVERRIDE)
green_to_green = self.current_phase in (TrafficAction.NS_GREEN, TrafficAction.EW_GREEN, TrafficAction.LEFT_PRIORITY)
wants_green = action in (TrafficAction.NS_GREEN, TrafficAction.EW_GREEN, TrafficAction.LEFT_PRIORITY)
if switching and green_to_green and wants_green and self.time_since_switch < min_green:
diagnostics.unsafe_switch_penalty += 1
diagnostics.notes.append("Minimum green-time violation.")
if action == TrafficAction.PEDESTRIAN_CROSS and self.pedestrian_count == 0:
diagnostics.unsafe_switch_penalty += 1
diagnostics.notes.append("Pedestrian phase requested without demand.")
if action == TrafficAction.EMERGENCY_OVERRIDE and not self.emergency.present:
diagnostics.unsafe_switch_penalty += 1
diagnostics.notes.append("Emergency override requested without emergency vehicle.")
if action == TrafficAction.EXTEND_GREEN:
if self.current_phase in (TrafficAction.NS_GREEN, TrafficAction.EW_GREEN, TrafficAction.LEFT_PRIORITY):
return self.current_phase
diagnostics.notes.append("EXTEND_GREEN from non-green phase converted to ALL_RED.")
return TrafficAction.ALL_RED
return action
def _maybe_switch_phase(self, action: TrafficAction) -> None:
if action != self.current_phase:
self.current_phase = action
self.time_since_switch = 0
def _clear_traffic(self, action: TrafficAction) -> int:
if action == TrafficAction.ALL_RED or action == TrafficAction.PEDESTRIAN_CROSS:
return 0
lanes = self._active_lanes(action)
if not lanes:
return 0
cleared = 0
rain_factor = 1.0 - self.rain_level * 0.32
blockage_factor = 0.45 if self.rng.random() < self.random_blockage_probability else 1.0
aggression_bonus = 1.0 + self.driver_aggression * 0.18
capacity_units = 8.5 * rain_factor * blockage_factor * aggression_bonus
if action == TrafficAction.LEFT_PRIORITY:
capacity_units *= 0.65
if action == TrafficAction.EMERGENCY_OVERRIDE:
capacity_units *= 1.15
for lane in lanes:
remaining_units = capacity_units
for vehicle in ("bikes", "autos", "cars", "buses", "trucks"):
cleared_count, remaining_units = self._clear_vehicle_type(lane, vehicle, remaining_units)
cleared += cleared_count
if self.queues[lane] and sum(self.queues[lane].values()) == 0:
self.waiting_time[lane] = 0.0
return cleared
def _clear_vehicle_type(self, lane: str, vehicle: str, remaining_units: float) -> Tuple[int, float]:
unit = VEHICLE_CLEARANCE_UNITS[vehicle]
possible = int(remaining_units // unit)
count = min(self.queues[lane][vehicle], possible)
self.queues[lane][vehicle] -= count
return count, remaining_units - count * unit
def _active_lanes(self, action: TrafficAction) -> Iterable[str]:
if action == TrafficAction.EMERGENCY_OVERRIDE and self.emergency.present and self.emergency.lane:
return (self.emergency.lane,)
return LANE_GROUPS.get(action, ())
def _maybe_spawn_emergency(self) -> None:
if self.emergency.present:
return
if self.rng.random() < float(self.task.constraints["emergency_rate"]):
self.emergency = EmergencyVehicle(
present=True,
lane=self.rng.choice(LANES),
type=self.rng.choice(["ambulance", "fire_truck"]),
wait_time=0.0,
)
self.metrics.emergency_seen += 1
def _update_emergency(self, action: TrafficAction) -> bool:
if not self.emergency.present or not self.emergency.lane:
return False
active = set(self._active_lanes(action))
if self.emergency.lane in active:
if action == TrafficAction.EMERGENCY_OVERRIDE or self.rng.random() < 0.55:
if self.emergency.wait_time <= 8:
self.metrics.emergency_cleared_fast += 1
self.emergency = EmergencyVehicle(present=False)
return True
self.emergency.wait_time += 1.0
return False
def _update_pedestrians(self, action: TrafficAction) -> None:
arrivals = 1 if self.rng.random() < 0.35 else 0
if self.rng.random() < 0.08 * self.peak_hour_multiplier:
arrivals += self.rng.randint(1, 3)
self.pedestrian_count += arrivals
if action == TrafficAction.PEDESTRIAN_CROSS:
crossed = min(self.pedestrian_count, 18)
self.pedestrian_count -= crossed
if self.pedestrian_count == 0:
self.pedestrian_wait_time = 0.0
return
if self.pedestrian_count:
unsafe_crossing_pressure = self.driver_aggression * self.pedestrian_wait_time / 60.0
if self.rng.random() < unsafe_crossing_pressure:
self.pedestrian_count = max(0, self.pedestrian_count - 1)
self.pedestrian_wait_time += self.pedestrian_count * 0.55
def _update_waiting_times(self) -> None:
active = set(self._active_lanes(self.current_phase))
for lane in LANES:
queue = sum(self.queues[lane].values())
if queue == 0:
self.waiting_time[lane] = 0.0
continue
pressure = queue * (1.0 + self.rain_level * 0.3)
if lane in active:
pressure *= 0.35
self.waiting_time[lane] += pressure
def _calculate_reward(
self,
vehicles_cleared: int,
total_waiting_time: float,
queue_length: int,
pedestrian_wait_time: float,
unsafe_switch_penalty: int,
emergency_clear_bonus: int,
diagnostics: StepDiagnostics,
) -> float:
weights = self.task.reward_weights
raw = (
vehicles_cleared * weights["vehicles_cleared"]
+ total_waiting_time * weights["total_waiting_time"]
+ queue_length * weights["queue_length"]
+ pedestrian_wait_time * weights["pedestrian_wait_time"]
+ unsafe_switch_penalty * weights["unsafe_switch_penalty"]
+ emergency_clear_bonus * weights["emergency_clear_bonus"]
)
if queue_length == 0:
raw += 10.0
diagnostics.notes.append("Full clearance milestone.")
if diagnostics.invalid_action:
raw -= 8.0
diagnostics.raw_reward = raw
normalized = max(0.0, min(1.0, (raw + 180.0) / 260.0))
diagnostics.normalized_reward = normalized
if unsafe_switch_penalty:
self.metrics.unsafe_switches += unsafe_switch_penalty
return normalized
def _total_queue_length(self) -> int:
return sum(sum(queue.values()) for queue in self.queues.values())
def _is_done(self, queue_length: int) -> bool:
if self.tick + 1 >= int(self.task.constraints["max_steps"]):
return True
if self.metrics.total_vehicles_cleared >= int(self.task.termination["target_cleared"]):
return True
if queue_length >= int(self.task.constraints["max_queue_before_failure"]):
return True
max_emergency_wait = self.task.termination.get("max_emergency_wait")
if max_emergency_wait and self.emergency.present and self.emergency.wait_time > float(max_emergency_wait):
return True
return False
def _info(self, diagnostics: StepDiagnostics) -> Dict[str, object]:
total_wait = sum(self.waiting_time.values())
return {
"task_id": self.task_id,
"vehicles_cleared": diagnostics.vehicles_cleared,
"total_vehicles_cleared": self.metrics.total_vehicles_cleared,
"total_waiting_time": round(total_wait, 3),
"queue_length": self._total_queue_length(),
"unsafe_switch_penalty": diagnostics.unsafe_switch_penalty,
"emergency_clear_bonus": diagnostics.emergency_clear_bonus,
"raw_reward": round(diagnostics.raw_reward, 3),
"normalized_reward": round(diagnostics.normalized_reward, 3),
"hidden_dynamics": {
"driver_aggression": round(self.driver_aggression, 3),
"random_blockage_probability": round(self.random_blockage_probability, 3),
"peak_hour_multiplier": round(self.peak_hour_multiplier, 3),
},
"notes": diagnostics.notes,
}