Automated highway system

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An automated highway system (AHS) or Smart Road, is an advanced Intelligent transportation system technology designed to provide for driverless cars on specific rights-of-way. It is most often touted as a means of traffic congestion relief, since it drastically reduces following distances and thus allow more cars to occupy a given stretch of road.

How it works

The roadway has magnetized stainless-steel spikes driven one meter apart in its center. The car senses the spikes to measure its speed and locate the center of the lane. Further the spikes can have either magnetic north or magnetic south facing up. The roadway thus has small amounts of digital data describing interchanges, recommended speeds, etc.

The cars have power steering, and automatic speed controls, but these are controlled by the computer.

The cars organize themselves into platoons of eight to twenty-five cars. The platoons drive themselves a meter apart, so that air resistance is minimized. The distance between platoons is the conventional braking distance. If anything goes wrong, the maximum number of harmed cars should be one platoon.

Deployments

A prototype automated highway system was tested in San Diego County, California along Interstate 15. However, despite the technical success of the program, investment has moved more toward autonomous intelligent vehicles rather than building specialized infrastructure. The AHS system places sensory technology in cars that can read passive road markings, and use radar and inter-car communications to make the cars organize themselves without the intervention of drivers.

Policy issues

The difficulty of AHS deployment is the chicken-and-egg problem: no one will buy AHS equipped cars unless there is a network that can accommodate them (and only them), and no one will build the network until there are sufficient number of AHS vehicles on the road. AHS cannot mix with regular traffic. For this reason, most ITS research is aiming for intelligent vehicles or smart cars. Those cars can assist the driver in mixed traffic (including traditional non-smart cars), and are thus likely to be deployed sooner.

Economist Anthony Downs (Still Stuck in Traffic, 2004) has pointed out that while engineers have generally done an excellent job in developing automated highways and control systems, they have not given much thought to the implications of having several times as many cars on a piece of road as is possible with manual control. Freeway interchanges would have to be rebuilt, and enormous parking garages would be required to accommodate the massively increased number of cars. Traffic accidents would almost invariably cause multiple fatalities on a highway where tightly packed cars are moving at 70 mph (114 km/h), creating the potential for market failure in the automobile insurance sector. If safety mandates were revised to require cars to be 99% crash-survivable at such a high speed, automobile weights would increase dramatically, causing a significant increase in fuel consumption that would bring its own set of unpleasant consequences.

Since auto safety is mainly a control problem, one can assume that electronic systems will eventually take the place of passive safety design. However, because of the aforementioned chicken-and-egg and liability problems, it is unlikely that automated highway systems will see much use, atleast not in the near future.it:Autostrade automatizzate