Car Counter

Hi There,
I was wondering if anyone can help me with a subject.

I need to know information on how to design a car counter to count how many cars enter a ca park. I would use a counter to count how many cars are in the car park and if the car park was full it would display to the next driver the car park is full. I would also want to use a display system to show how many spaces are left.

Any information would be helpful or any ideas.
thanks

u have to use infrared LEDs, counter ICs (i dont remember numbers now).
u r going to use 2 infrared for counting.1st infrared will make a count or it will sense the blocking to its respective tranmitter due to car and other will judge the direction of car i.e. car is entering or leaving the parking. my exams r going on now.if this is not enough plz do tell me (personal messege me). i will to give u the circuit diagram even, if i found it