automatic traffic light controller using basic gates according to density

[Guest]

hi...can any one suggest me how to design an automated traffic control signal for four directions using Basic gates considering the density on 4 directions i.e, the time for which green or red lights occur is dependent on the density of traffic on that side. density is divided into three low,medium and high...so for four directions we get 81 possible cases....for eg: LLHH means the green light should be for 10,10,20,20 sec respectively.(everytime the cycle time being constant i.e,60 sec for each cycle) and so on..