100% Code

using System;
using System.Linq;
using System.Collections.Generic;

namespace crossroads
{
    class Program
    {
        static void Main(string[] args)
        {
            int greenLight = int.Parse(Console.ReadLine());
            int window = int.Parse(Console.ReadLine());
            Queue<string> cars = new Queue<string>();
            int carCounter = 0;
            bool carCrash = false;

            string command = Console.ReadLine();

            while (command.ToUpper() != "END")
            {
                if (command.ToLower() == "green")
                {
                    int currentLight = greenLight;

                    string currentCar = string.Empty;

                    while (currentLight > 0)
                    {
                        if (cars.Count > 0)
                        {
                            currentCar = cars.Dequeue();

                            if (currentLight - currentCar.Length < 0)
                            {
                                if (currentLight - currentCar.Length + window >= 0)
                                {
                                    carCounter++;
                                    break;
                                }
                                else
                                {
                                    char hitCharacter = currentCar[currentLight + window];
                                    Console.WriteLine("A crash happened!");
                                    Console.WriteLine($"{currentCar} was hit at {hitCharacter}.");
                                    carCrash = true;
                                    break;

                                }
                            }

                            currentLight -= currentCar.Length;
                            carCounter++;
                        }
                        else
                        {
                            break;
                        }
                    }
                }
                else
                {
                    cars.Enqueue(command);
                }

                if (carCrash)
                {
                    break;
                }

                command = Console.ReadLine();
            }

            if (carCrash == false)
            {
                Console.WriteLine("Everyone is safe.");
                Console.WriteLine($"{carCounter} total cars passed the crossroads.");
            }
        }
    }
}

;-)