Social engineering is merging with traffic engineering, creating new technologies that charge people a variable toll based on how many cars are on the road -- known as congestion pricing -- or reduce toll rates for high occupancy to encourage car-pooling. It is shaping up as one of the biggest philosophical changes in transportation policy since the toll-free interstate highway system was created under President Dwight D. Eisenhower in 1956. Paying on the Highway to Get Out of First Gear | 
