Grouping vehicles into platoons is a method of increasing the capacity of roads. An automated highway system is a proposed technology for doing this. Platoons decrease the distances between cars using electronic, and possibly mechanical, coupling. This capability would allow many cars to accelerate or brake simultaneously. Instead of waiting after a traffic light changes to green for drivers ahead to react, a synchronized platoon would move as one, allowing up to a fivefold increase in traffic throughput.
This system also allows for a closer headway between vehicles by eliminating reacting distance needed for human reaction. Platoon capability might require buying new cars, or it may be something that can be retrofitted. Drivers would probably need a special license endorsement on account of the new skills required and the added responsibility when driving in the lead. Smart cars with artificial intelligence could automatically join and leave platoons. In the automated highway system proposal, cars organize themselves into platoons of eight to twenty-five.