Automated Highway Systems
A major long-term element of Intelligent Transportation Systems research and development is
Automated highway Systems (AHS). The AHS program is a broad international effort “to provide the basis for, and transition to, the next major performance upgrade of the vehicle/highway system through the use of automated vehicle control technology” [NAHSC96].
The detailed definition of the Automated Highway System is as follows [Plan93]:
The term “fully automated intelligent vehicle-highway system” is interpreted to mean a system that: w Evolves from today’s roads (beginning in selected corridors); w P rovides fully automated “hands-off” operation at better levels of performance than today’s roadways in terms of safety, efficiency, and operator comfort; and, w A llows equipped vehicles to operate in both urban and rural areas on highways that are both instrumented, and not instrumented.
The consensus in the AHS community is that AHS will evolve over a series of smaller steps in technology. The final step of full automation will not be a leap, but a logical consequence of previous development and deployment efforts. Each step in the technology will have its own benefits and be self-sustaining. Vehicle and infrastructure evolutions will be “synchronous”
[James94]. We will briefly mention the steps of this evolution here before introducing the AHS program and discussing automatic vehicle control technologies in detail.
When the cruise control was first developed, there was much concern over the safety and user acceptance of the new system; however, it has become widely accepted and used. In the near future, obstacle and headway warning and Automatic Vehicle Identification (AVI) will be added to modern cruise control and existing communications infrastructure. The success of AHS depends on linking the power of cellular communications and the emerging range of highperformance computers to the ongoing vehicle based