Traffic Congestion in Oakland County

Our roads are becoming more congested because the volumes of traffic using the roads often exceed the capacity of those roads. Why not just get the traffic moving much faster so that you get that many more vehicles through an area in an hour?

If you look at the traffic engineering textbooks, you find that the optimal speed for moving traffic on a lane of roadway to get the highest number of vehicles through an area is about 32 mph. So why not increase in the speed and get even more through?

Because it is important to maintain a safe stopping distance between vehicles, and as you increase the speed, that distance also increases. At 32 mph, it is theoretically possible to move about 2,000 vehicles per hour on one lane of pavement. Any faster or slower and the number is less than 2,000.

What Causes Congestion

In reality, however, we move more than 2,000 vehicles an hour on some of our major roads. How is that possible?

Because people frequently follow the car ahead much too closely for the speed they are travelling. This also partially explains why we have so many rear-end accidents.

Obviously, if we could figure out a way to safely run vehicles very closely together at high speeds, we would do a lot to solve our road capacity problems. Actually, there is ongoing research in this area.

Intelligent Transportation Systems

In the area of Intelligent Transportation Systems (ITS), much research is taking place on such subjects as collision-avoidance technology that may someday allow this. RCOC also has been using technology since 1992 to help improve the efficiency of intersections on busy county roads, through its FAST-TRAC program.

FAST-TRAC (Faster and Safer Travel through Traffic Routing and Advanced Controls) uses either video imaging devices or pavement “loops” connected to computers to continuously monitor the flow of traffic through an intersection. The video imaging devices use video images of the intersection to automatically count vehicles in the intersection. The loops are wires buried in the intersection pavement which sense the number of vehicles driving over them.

Both methods send second-by-second data to a computer which then adjusts the signal cycle in “real time” to best meet the demand present at that moment. Studies by objective third parties, such as Michigan State University, have concluded that the FAST-TRAC system is reducing the amount of time motorists wait in traffic jams at busy intersections. The program, however, cannot completely eliminate congestion at intersections where the traffic volume exceeds the roadway capacity.