This is my second Arduino project - Very simple traffic light http://youtu.be/HAurB9fVTWM

traffic1.ino

/*
  Copyright (c) 2013 ik_5 <[email protected]>

  Permission is hereby granted, free of charge, to any person obtaining a copy of this 
  software and associated documentation files (the "Software"), to deal in the Software 
  without restriction, including without limitation the rights to use, copy, modify, 
  merge, publish, distribute, sublicense, and/or sell copies of the Software, and to 
  permit persons to whom the Software is furnished to do so, subject to the following 
  conditions:

  The above copyright notice and this permission notice shall be included in all copies or 
  substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
  PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT 
  OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 
  OTHER DEALINGS IN THE SOFTWARE.
*/

const int GreenLed  = 12;
const int YellowLed = 11;
const int RedLed    = 10;

int state     = 0; // State 0 - Red only, State 1 - Red Yellow, State 2 - Green
                   // State 3 - Yellow
int light_delay[]   = { 2500, 500, 2500, 500 };

void setup() {
	pinMode(GreenLed, OUTPUT);
	pinMode(YellowLed,OUTPUT);
	pinMode(RedLed,OUTPUT);
}

void loop() {
   switch (state) {
	   case 0 : 
	      digitalWrite(YellowLed, LOW);
              digitalWrite(RedLed, HIGH); 
	      break;
	   case 1 :
              digitalWrite(YellowLed, HIGH);
	      break;
	   case 2 :
	      digitalWrite(YellowLed, LOW);
              digitalWrite(RedLed, LOW); 
              digitalWrite(GreenLed, HIGH);
	      break;
	   case 3 :
	      digitalWrite(GreenLed, LOW);
	      digitalWrite(YellowLed, HIGH);
	      break;
   }
   
   delay(light_delay[state]);
   
   if (state == 3) {
	   state = 0;
   } else {
	   state += 1;
   }	
}