Ramp control strategies and geometric design implications of high-speed automated transportation systems

Abstract

In recent years, the field of transportation engineering has witnessed the emergence of technological innovations linking several different application areas like human factors, computer science, communications and operations research. This research deals with automatic freeway traffic operations including ramp guidance and merging which is an important aspect of Intelligent Vehicle Highway Systems (VHS) Technology. An existing traffic flow model is utilized to generate a non-overtaking, continuous traffic stream with automatic acceleration/ deceleration characteristics of the smart cars to fulfill the needs of a high-speed flow under controlled headway and optimized density conditions.

The orientation, shape, and geometry of such ramps on a high-speed highway system is investigated. It is proposed that the angle between the ramp and highway would be very acute and lane changes from acceleration lane to the cruising lane would follow a smooth trajectory. The curve would be composed of two circular curves of large radii of curvature or two spiral curves in succession.

The adequacy of the existing geometric design specifications are questionable, not only for the merging section, but the entire stretch of the "smart highway”. The introduction of intelligent highway network extensively in rural areas could necessitate a complete rethinking about highway geometric design standards. An alternate method of geometric design requirements is undertaken to explore the applications of vehicle aerodynamics’ principles to the highway design, which is perceived to be essential under the high-speed conditions. The results obtained can be compared to those of the conventional geometric design formulae to yield a comparison. Though the principal aim of this research is to serve the highways, it has applicability to other forms of highspeed, controlled guideway transportation systems also.