22. Implement Behavior Planner in C++ (solution)

#include "vehicle.h"
#include <algorithm>
#include <iterator>
#include <map>
#include <string>
#include <vector>
#include "cost.h"

using std::string;
using std::vector;

// Initializes Vehicle
Vehicle::Vehicle(){}

Vehicle::Vehicle(int lane, float s, float v, float a, string state) {
  this->lane = lane;
  this->s = s;
  this->v = v;
  this->a = a;
  this->state = state;
  max_acceleration = -1;
}

Vehicle::~Vehicle() {}

vector<Vehicle> Vehicle::choose_next_state(map<int, vector<Vehicle>> &predictions) {
  /**
   * Here you can implement the transition_function code from the Behavior 
   *   Planning Pseudocode classroom concept.
   *
   * @param A predictions map. This is a map of vehicle id keys with predicted
   *   vehicle trajectories as values. Trajectories are a vector of Vehicle 
   *   objects representing the vehicle at the current timestep and one timestep
   *   in the future.
   * @output The best (lowest cost) trajectory corresponding to the next ego 
   *   vehicle state.
   *
   * Functions that will be useful:
   * 1. successor_states - Uses the current state to return a vector of possible
   *    successor states for the finite state machine.
   * 2. generate_trajectory - Returns a vector of Vehicle objects representing 
   *    a vehicle trajectory, given a state and predictions. Note that 
   *    trajectory vectors might have size 0 if no possible trajectory exists 
   *    for the state. 
   * 3. calculate_cost - Included from cost.cpp, computes the cost for a trajectory.
   *
   * TODO: Your solution here.
   */
  vector<string> states = successor_states();
  float cost;
  vector<float> costs;
  vector<vector<Vehicle>> final_trajectories;

  for (vector<string>::iterator it = states.begin(); it != states.end(); ++it) {
    vector<Vehicle> trajectory = generate_trajectory(*it, predictions);
    if (trajectory.size() != 0) {
      cost = calculate_cost(*this, predictions, trajectory);
      costs.push_back(cost);
      final_trajectories.push_back(trajectory);
    }
  }

  vector<float>::iterator best_cost = min_element(begin(costs), end(costs));
  int best_idx = distance(begin(costs), best_cost);

  /**
   * TODO: Change return value here:
   */
  return final_trajectories[best_idx];
}

vector<string> Vehicle::successor_states() {
  // Provides the possible next states given the current state for the FSM 
  //   discussed in the course, with the exception that lane changes happen 
  //   instantaneously, so LCL and LCR can only transition back to KL.
  vector<string> states;
  states.push_back("KL");
  string state = this->state;
  if(state.compare("KL") == 0) {
    states.push_back("PLCL");
    states.push_back("PLCR");
  } else if (state.compare("PLCL") == 0) {
    if (lane != lanes_available - 1) {
      states.push_back("PLCL");
      states.push_back("LCL");
    }
  } else if (state.compare("PLCR") == 0) {
    if (lane != 0) {
      states.push_back("PLCR");
      states.push_back("LCR");
    }
  }
    
  // If state is "LCL" or "LCR", then just return "KL"
  return states;
}

vector<Vehicle> Vehicle::generate_trajectory(string state, 
                                             map<int, vector<Vehicle>> &predictions) {
  // Given a possible next state, generate the appropriate trajectory to realize
  //   the next state.
  vector<Vehicle> trajectory;
  if (state.compare("CS") == 0) {
    trajectory = constant_speed_trajectory();
  } else if (state.compare("KL") == 0) {
    trajectory = keep_lane_trajectory(predictions);
  } else if (state.compare("LCL") == 0 || state.compare("LCR") == 0) {
    trajectory = lane_change_trajectory(state, predictions);
  } else if (state.compare("PLCL") == 0 || state.compare("PLCR") == 0) {
    trajectory = prep_lane_change_trajectory(state, predictions);
  }

  return trajectory;
}

vector<float> Vehicle::get_kinematics(map<int, vector<Vehicle>> &predictions, 
                                      int lane) {
  // Gets next timestep kinematics (position, velocity, acceleration) 
  //   for a given lane. Tries to choose the maximum velocity and acceleration, 
  //   given other vehicle positions and accel/velocity constraints.
  float max_velocity_accel_limit = this->max_acceleration + this->v;
  float new_position;
  float new_velocity;
  float new_accel;
  Vehicle vehicle_ahead;
  Vehicle vehicle_behind;

  if (get_vehicle_ahead(predictions, lane, vehicle_ahead)) {
    if (get_vehicle_behind(predictions, lane, vehicle_behind)) {
      // must travel at the speed of traffic, regardless of preferred buffer
      new_velocity = vehicle_ahead.v;
    } else {
      float max_velocity_in_front = (vehicle_ahead.s - this->s 
                                  - this->preferred_buffer) + vehicle_ahead.v 
                                  - 0.5 * (this->a);
      new_velocity = std::min(std::min(max_velocity_in_front, 
                                       max_velocity_accel_limit), 
                                       this->target_speed);
    }
  } else {
    new_velocity = std::min(max_velocity_accel_limit, this->target_speed);
  }
    
  new_accel = new_velocity - this->v; // Equation: (v_1 - v_0)/t = acceleration
  new_position = this->s + new_velocity + new_accel / 2.0;
    
  return{new_position, new_velocity, new_accel};
}

vector<Vehicle> Vehicle::constant_speed_trajectory() {
  // Generate a constant speed trajectory.
  float next_pos = position_at(1);
  vector<Vehicle> trajectory = {Vehicle(this->lane,this->s,this->v,this->a,this->state), 
                                Vehicle(this->lane,next_pos,this->v,0,this->state)};
  return trajectory;
}

vector<Vehicle> Vehicle::keep_lane_trajectory(map<int, vector<Vehicle>> &predictions) {
  // Generate a keep lane trajectory.
  vector<Vehicle> trajectory = {Vehicle(lane, this->s, this->v, this->a, state)};
  vector<float> kinematics = get_kinematics(predictions, this->lane);
  float new_s = kinematics[0];
  float new_v = kinematics[1];
  float new_a = kinematics[2];
  trajectory.push_back(Vehicle(this->lane, new_s, new_v, new_a, "KL"));
  
  return trajectory;
}

vector<Vehicle> Vehicle::prep_lane_change_trajectory(string state, 
                                                     map<int, vector<Vehicle>> &predictions) {
  // Generate a trajectory preparing for a lane change.
  float new_s;
  float new_v;
  float new_a;
  Vehicle vehicle_behind;
  int new_lane = this->lane + lane_direction[state];
  vector<Vehicle> trajectory = {Vehicle(this->lane, this->s, this->v, this->a, 
                                        this->state)};
  vector<float> curr_lane_new_kinematics = get_kinematics(predictions, this->lane);

  if (get_vehicle_behind(predictions, this->lane, vehicle_behind)) {
    // Keep speed of current lane so as not to collide with car behind.
    new_s = curr_lane_new_kinematics[0];
    new_v = curr_lane_new_kinematics[1];
    new_a = curr_lane_new_kinematics[2];    
  } else {
    vector<float> best_kinematics;
    vector<float> next_lane_new_kinematics = get_kinematics(predictions, new_lane);
    // Choose kinematics with lowest velocity.
    if (next_lane_new_kinematics[1] < curr_lane_new_kinematics[1]) {
      best_kinematics = next_lane_new_kinematics;
    } else {
      best_kinematics = curr_lane_new_kinematics;
    }
    new_s = best_kinematics[0];
    new_v = best_kinematics[1];
    new_a = best_kinematics[2];
  }

  trajectory.push_back(Vehicle(this->lane, new_s, new_v, new_a, state));
  
  return trajectory;
}

vector<Vehicle> Vehicle::lane_change_trajectory(string state, 
                                                map<int, vector<Vehicle>> &predictions) {
  // Generate a lane change trajectory.
  int new_lane = this->lane + lane_direction[state];
  vector<Vehicle> trajectory;
  Vehicle next_lane_vehicle;
  // Check if a lane change is possible (check if another vehicle occupies 
  //   that spot).
  for (map<int, vector<Vehicle>>::iterator it = predictions.begin(); 
       it != predictions.end(); ++it) {
    next_lane_vehicle = it->second[0];
    if (next_lane_vehicle.s == this->s && next_lane_vehicle.lane == new_lane) {
      // If lane change is not possible, return empty trajectory.
      return trajectory;
    }
  }
  trajectory.push_back(Vehicle(this->lane, this->s, this->v, this->a, 
                               this->state));
  vector<float> kinematics = get_kinematics(predictions, new_lane);
  trajectory.push_back(Vehicle(new_lane, kinematics[0], kinematics[1], 
                               kinematics[2], state));
  return trajectory;
}

void Vehicle::increment(int dt = 1) {
  this->s = position_at(dt);
}

float Vehicle::position_at(int t) {
  return this->s + this->v*t + this->a*t*t/2.0;
}

bool Vehicle::get_vehicle_behind(map<int, vector<Vehicle>> &predictions, 
                                 int lane, Vehicle &rVehicle) {
  // Returns a true if a vehicle is found behind the current vehicle, false 
  //   otherwise. The passed reference rVehicle is updated if a vehicle is found.
  int max_s = -1;
  bool found_vehicle = false;
  Vehicle temp_vehicle;
  for (map<int, vector<Vehicle>>::iterator it = predictions.begin(); 
       it != predictions.end(); ++it) {
    temp_vehicle = it->second[0];
    if (temp_vehicle.lane == this->lane && temp_vehicle.s < this->s 
        && temp_vehicle.s > max_s) {
      max_s = temp_vehicle.s;
      rVehicle = temp_vehicle;
      found_vehicle = true;
    }
  }
  
  return found_vehicle;
}

bool Vehicle::get_vehicle_ahead(map<int, vector<Vehicle>> &predictions, 
                                int lane, Vehicle &rVehicle) {
  // Returns a true if a vehicle is found ahead of the current vehicle, false 
  //   otherwise. The passed reference rVehicle is updated if a vehicle is found.
  int min_s = this->goal_s;
  bool found_vehicle = false;
  Vehicle temp_vehicle;
  for (map<int, vector<Vehicle>>::iterator it = predictions.begin(); 
       it != predictions.end(); ++it) {
    temp_vehicle = it->second[0];
    if (temp_vehicle.lane == this->lane && temp_vehicle.s > this->s 
        && temp_vehicle.s < min_s) {
      min_s = temp_vehicle.s;
      rVehicle = temp_vehicle;
      found_vehicle = true;
    }
  }
  
  return found_vehicle;
}

vector<Vehicle> Vehicle::generate_predictions(int horizon) {
  // Generates predictions for non-ego vehicles to be used in trajectory 
  //   generation for the ego vehicle.
  vector<Vehicle> predictions;
  for(int i = 0; i < horizon; ++i) {
    float next_s = position_at(i);
    float next_v = 0;
    if (i < horizon-1) {
      next_v = position_at(i+1) - s;
    }
    predictions.push_back(Vehicle(this->lane, next_s, next_v, 0));
  }
  
  return predictions;
}

void Vehicle::realize_next_state(vector<Vehicle> &trajectory) {
  // Sets state and kinematics for ego vehicle using the last state of the trajectory.
  Vehicle next_state = trajectory[1];
  this->state = next_state.state;
  this->lane = next_state.lane;
  this->s = next_state.s;
  this->v = next_state.v;
  this->a = next_state.a;
}

void Vehicle::configure(vector<int> &road_data) {
  // Called by simulator before simulation begins. Sets various parameters which
  //   will impact the ego vehicle.
  target_speed = road_data[0];
  lanes_available = road_data[1];
  goal_s = road_data[2];
  goal_lane = road_data[3];
  max_acceleration = road_data[4];
}

#ifndef VEHICLE_H
#define VEHICLE_H

#include <map>
#include <string>
#include <vector>

using std::map;
using std::string;
using std::vector;

class Vehicle {
 public:
  // Constructors
  Vehicle();
  Vehicle(int lane, float s, float v, float a, string state="CS");

  // Destructor
  virtual ~Vehicle();

  // Vehicle functions
  vector<Vehicle> choose_next_state(map<int, vector<Vehicle>> &predictions);

  vector<string> successor_states();

  vector<Vehicle> generate_trajectory(string state, 
                                      map<int, vector<Vehicle>> &predictions);

  vector<float> get_kinematics(map<int, vector<Vehicle>> &predictions, int lane);

  vector<Vehicle> constant_speed_trajectory();

  vector<Vehicle> keep_lane_trajectory(map<int, vector<Vehicle>> &predictions);

  vector<Vehicle> lane_change_trajectory(string state, 
                                         map<int, vector<Vehicle>> &predictions);

  vector<Vehicle> prep_lane_change_trajectory(string state, 
                                              map<int, vector<Vehicle>> &predictions);

  void increment(int dt);

  float position_at(int t);

  bool get_vehicle_behind(map<int, vector<Vehicle>> &predictions, int lane, 
                          Vehicle &rVehicle);

  bool get_vehicle_ahead(map<int, vector<Vehicle>> &predictions, int lane, 
                         Vehicle &rVehicle);

  vector<Vehicle> generate_predictions(int horizon=2);

  void realize_next_state(vector<Vehicle> &trajectory);

  void configure(vector<int> &road_data);

  // public Vehicle variables
  struct collider{
    bool collision; // is there a collision?
    int  time; // time collision happens
  };

  map<string, int> lane_direction = {{"PLCL", 1}, {"LCL", 1}, 
                                     {"LCR", -1}, {"PLCR", -1}};

  int L = 1;

  int preferred_buffer = 6; // impacts "keep lane" behavior.

  int lane, s, goal_lane, goal_s, lanes_available;

  float v, target_speed, a, max_acceleration;

  string state;
};

#endif  // VEHICLE_H

#include "cost.h"
#include <cmath>
#include <functional>
#include <iterator>
#include <map>
#include <string>
#include <vector>
#include "vehicle.h"

using std::string;
using std::vector;

/**
 * TODO: change weights for cost functions.
 */
const float REACH_GOAL = pow(10, 6);
const float EFFICIENCY = pow(10, 5);

// Here we have provided two possible suggestions for cost functions, but feel 
//   free to use your own! The weighted cost over all cost functions is computed
//   in calculate_cost. The data from get_helper_data will be very useful in 
//   your implementation of the cost functions below. Please see get_helper_data
//   for details on how the helper data is computed.

float goal_distance_cost(const Vehicle &vehicle, 
                         const vector<Vehicle> &trajectory, 
                         const map<int, vector<Vehicle>> &predictions, 
                         map<string, float> &data) {
  // Cost increases based on distance of intended lane (for planning a lane 
  //   change) and final lane of trajectory.
  // Cost of being out of goal lane also becomes larger as vehicle approaches 
  //   goal distance.
  // This function is very similar to what you have already implemented in the 
  //   "Implement a Cost Function in C++" quiz.
  float cost;
  float distance = data["distance_to_goal"];
  if (distance > 0) {
    cost = 1 - 2*exp(-(abs(2.0*vehicle.goal_lane - data["intended_lane"] 
         - data["final_lane"]) / distance));
  } else {
    cost = 1;
  }

  return cost;
}

float inefficiency_cost(const Vehicle &vehicle, 
                        const vector<Vehicle> &trajectory, 
                        const map<int, vector<Vehicle>> &predictions, 
                        map<string, float> &data) {
  // Cost becomes higher for trajectories with intended lane and final lane 
  //   that have traffic slower than vehicle's target speed.
  // You can use the lane_speed function to determine the speed for a lane. 
  // This function is very similar to what you have already implemented in 
  //   the "Implement a Second Cost Function in C++" quiz.
  float proposed_speed_intended = lane_speed(predictions, data["intended_lane"]);
  if (proposed_speed_intended < 0) {
    proposed_speed_intended = vehicle.target_speed;
  }

  float proposed_speed_final = lane_speed(predictions, data["final_lane"]);
  if (proposed_speed_final < 0) {
    proposed_speed_final = vehicle.target_speed;
  }
    
  float cost = (2.0*vehicle.target_speed - proposed_speed_intended 
             - proposed_speed_final)/vehicle.target_speed;

  return cost;
}

float lane_speed(const map<int, vector<Vehicle>> &predictions, int lane) {
  // All non ego vehicles in a lane have the same speed, so to get the speed 
  //   limit for a lane, we can just find one vehicle in that lane.
  for (map<int, vector<Vehicle>>::const_iterator it = predictions.begin(); 
       it != predictions.end(); ++it) {
    int key = it->first;
    Vehicle vehicle = it->second[0];
    if (vehicle.lane == lane && key != -1) {
      return vehicle.v;
    }
  }
  // Found no vehicle in the lane
  return -1.0;
}

float calculate_cost(const Vehicle &vehicle, 
                     const map<int, vector<Vehicle>> &predictions, 
                     const vector<Vehicle> &trajectory) {
  // Sum weighted cost functions to get total cost for trajectory.
  map<string, float> trajectory_data = get_helper_data(vehicle, trajectory, 
                                                       predictions);
  float cost = 0.0;

  // Add additional cost functions here.
  vector<std::function<float(const Vehicle &, const vector<Vehicle> &, 
                             const map<int, vector<Vehicle>> &, 
                             map<string, float> &)
    >> cf_list = {goal_distance_cost, inefficiency_cost};
  vector<float> weight_list = {REACH_GOAL, EFFICIENCY};
    
  for (int i = 0; i < cf_list.size(); ++i) {
    float new_cost = weight_list[i]*cf_list[i](vehicle, trajectory, predictions, 
                                               trajectory_data);
    cost += new_cost;
  }

  return cost;
}

map<string, float> get_helper_data(const Vehicle &vehicle, 
                                   const vector<Vehicle> &trajectory, 
                                   const map<int, vector<Vehicle>> &predictions) {
  // Generate helper data to use in cost functions:
  // intended_lane: the current lane +/- 1 if vehicle is planning or 
  //   executing a lane change.
  // final_lane: the lane of the vehicle at the end of the trajectory.
  // distance_to_goal: the distance of the vehicle to the goal.

  // Note that intended_lane and final_lane are both included to help 
  //   differentiate between planning and executing a lane change in the 
  //   cost functions.
  map<string, float> trajectory_data;
  Vehicle trajectory_last = trajectory[1];
  float intended_lane;

  if (trajectory_last.state.compare("PLCL") == 0) {
    intended_lane = trajectory_last.lane + 1;
  } else if (trajectory_last.state.compare("PLCR") == 0) {
    intended_lane = trajectory_last.lane - 1;
  } else {
    intended_lane = trajectory_last.lane;
  }

  float distance_to_goal = vehicle.goal_s - trajectory_last.s;
  float final_lane = trajectory_last.lane;
  trajectory_data["intended_lane"] = intended_lane;
  trajectory_data["final_lane"] = final_lane;
  trajectory_data["distance_to_goal"] = distance_to_goal;
    
  return trajectory_data;
}

#ifndef COST_H
#define COST_H

#include "vehicle.h"

using std::map;
using std::string;
using std::vector;

float calculate_cost(const Vehicle &vehicle, 
                     const map<int, vector<Vehicle>> &predictions, 
                     const vector<Vehicle> &trajectory);

float goal_distance_cost(const Vehicle &vehicle,  
                         const vector<Vehicle> &trajectory,  
                         const map<int, vector<Vehicle>> &predictions, 
                         map<string, float> &data);

float inefficiency_cost(const Vehicle &vehicle, 
                        const vector<Vehicle> &trajectory, 
                        const map<int, vector<Vehicle>> &predictions, 
                        map<string, float> &data);

float lane_speed(const map<int, vector<Vehicle>> &predictions, int lane);

map<string, float> get_helper_data(const Vehicle &vehicle, 
                                   const vector<Vehicle> &trajectory, 
                                   const map<int, vector<Vehicle>> &predictions);

#endif  // COST_H

#include <iostream>
#include <iterator>
#include <map>
#include <sstream>
#include <string>
#include <vector>
#include "road.h"
#include "vehicle.h"

using std::map;
using std::string;
using std::vector;

// Initializes Road
Road::Road(int speed_limit, double traffic_density, vector<int> &lane_speeds) {
  this->num_lanes = lane_speeds.size();
  this->lane_speeds = lane_speeds;
  this->speed_limit = speed_limit;
  this->density = traffic_density;
  this->camera_center = this->update_width/2;
}

Road::~Road() {}

Vehicle Road::get_ego() {
  return this->vehicles.find(this->ego_key)->second;
}

void Road::populate_traffic() {
  int start_s = std::max(this->camera_center - (this->update_width/2), 0);

  for (int l = 0; l < this->num_lanes; ++l) {
    int lane_speed = this->lane_speeds[l];
    bool vehicle_just_added = false;

    for (int s = start_s; s < start_s+this->update_width; ++s) {
      if (vehicle_just_added) {
        vehicle_just_added = false;
      }
      
      if (((double) rand() / (RAND_MAX)) < this->density) {
        Vehicle vehicle = Vehicle(l,s,lane_speed,0);
        vehicle.state = "CS";
        this->vehicles_added += 1;
        this->vehicles.insert(std::pair<int,Vehicle>(vehicles_added,vehicle));
        vehicle_just_added = true;
      }
    }
  }
}

void Road::advance() {
  map<int ,vector<Vehicle> > predictions;

  map<int, Vehicle>::iterator it = this->vehicles.begin();

  while (it != this->vehicles.end()) {
    int v_id = it->first;
    vector<Vehicle> preds = it->second.generate_predictions();
    predictions[v_id] = preds;
    ++it;
  }
  
  it = this->vehicles.begin();

  while (it != this->vehicles.end()) {
    int v_id = it->first;
    if (v_id == ego_key) {   
      vector<Vehicle> trajectory = it->second.choose_next_state(predictions);
      it->second.realize_next_state(trajectory);
    } else {
      it->second.increment(1);
    }
    ++it;
  }   
}

void Road::add_ego(int lane_num, int s, vector<int> &config_data) {
  map<int, Vehicle>::iterator it = this->vehicles.begin();

  while (it != this->vehicles.end()) {
    int v_id = it->first;
    Vehicle v = it->second;
    if (v.lane == lane_num && v.s == s) {
      this->vehicles.erase(v_id);
    }
    ++it;
  }
    
  Vehicle ego = Vehicle(lane_num, s, this->lane_speeds[lane_num], 0);
  ego.configure(config_data);
  ego.state = "KL";
  this->vehicles.insert(std::pair<int,Vehicle>(ego_key,ego));
}

void Road::display(int timestep) {
  Vehicle ego = this->vehicles.find(this->ego_key)->second;
  int s = ego.s;
  string state = ego.state;

  this->camera_center = std::max(s, this->update_width/2);
  int s_min = std::max(this->camera_center - this->update_width/2, 0);
  int s_max = s_min + this->update_width;

  vector<vector<string>> road;

  for (int i = 0; i < this->update_width; ++i) {
    vector<string> road_lane;
    for (int ln = 0; ln < this->num_lanes; ++ln) {
      road_lane.push_back("     ");
    }
    road.push_back(road_lane);
  }

  map<int, Vehicle>::iterator it = this->vehicles.begin();

  while (it != this->vehicles.end()) {
    int v_id = it->first;
    Vehicle v = it->second;

    if (s_min <= v.s && v.s < s_max) {
      string marker = "";

      if (v_id == this->ego_key) {
        marker = this->ego_rep;
      } else {
        std::stringstream oss;
        std::stringstream buffer;
        buffer << " ";
        oss << v_id;

        for (int buffer_i = oss.str().length(); buffer_i < 3; ++buffer_i) {
          buffer << "0";
        }
        buffer << oss.str() << " ";
        marker = buffer.str();
      }
      road[int(v.s - s_min)][int(v.lane)] = marker;
    }
    ++it;
  }
    
  std::ostringstream oss;
  oss << "+Meters ======================+ step: " << timestep << std::endl;
  int i = s_min;

  for (int lj = 0; lj < road.size(); ++lj) {
    if (i%20 ==0) {
      std::stringstream buffer;
      std::stringstream dis;
      dis << i;
      
      for (int buffer_i = dis.str().length(); buffer_i < 3; ++buffer_i) {
        buffer << "0";
      }
      
      oss << buffer.str() << dis.str() << " - ";
    } else {
      oss << "      ";
    }          
    ++i;
    for (int li = 0; li < road[0].size(); ++li) {
      oss << "|" << road[lj][li];
    }
      oss << "|";
      oss << "\n";
  }

  std::cout << oss.str();
}

#ifndef ROAD_H
#define ROAD_H

#include <map>
#include <string>
#include <vector>
#include "vehicle.h"

class Road {
 public:
  // Constructor
  Road(int speed_limit, double traffic_density, std::vector<int> &lane_speeds);

  // Destructor
  virtual ~Road();

  // Road functions
  Vehicle get_ego();

  void populate_traffic();

  void advance();

  void display(int timestep);

  void add_ego(int lane_num, int s, std::vector<int> &config_data);

  void cull();

  // Road variables
  int update_width = 70;

  int vehicles_added = 0;

  int ego_key = -1;

  int num_lanes, speed_limit, camera_center;

  double density; 

  std::map<int, Vehicle> vehicles;

  std::string ego_rep = " *** ";

  std::vector<int> lane_speeds; 
};

#endif  // ROAD_H