Intelligent Transportation Systems: Roadway Applications

Intelligent Transportation Systems (ITS) is a new field, encompassing all modes of transportation of people and goods. The focus of this chapter is on intelligent road transportation and on the role of control technologies in this interdisciplinary area. Two primary control-relevant topics in ITS are traffic control technologies and intelligent vehicles. The former can be further classified into street traffic and highways. Street traffic applications include signaling for both single intersections and networks of intersections, where the control variables are traffic light timings, and routing, in which traffic flow along different roads is manipulated to optimize some overall efficiency or congestion criterion. Highway traffic control applications range from the relatively mundane one of ramp control or metering to the exotic prospect of Automated Highway Systems (AHS) in which multiple vehicles operate as platoons. The grander visions of traffic control require a number of practical considerations to be addressed, including identification, sensing, and actuation over roadways with wireless networks. Intelligent vehicles require the incorporation within automobiles of intelligence and autonomy capabilities. (See Chapter 5 for a general discussion of intelligent control.) Limited autonomy is exhibited even in today's automobiles with cruise control and antilock braking systems???-???these loops automate throttle control and brake control. More meaningful autonomy requires closing a third loop, that of steering. (This requires a drive-by-wire capability that is currently lacking in production automobiles.) Furthermore, the overall problem must be considered a multivariable one. The chapter presents mathematical formulations and solution approaches for advanced cruise control, which includes automatic braking as well as acceleration, lane keeping with a s liding-mode-like nonlinear controller (Chapter 8 discusses sliding-mode control in detail), and lane changing.