Variation in the value of travel time savings and its impact on the benefits of managed lanes

This paper examines the variation in the value of travel time savings (VTTS) for travelers with a managed lane (ML) option when taking an ordinary trip versus a trip that is unusual in some way. VTTS estimates vary substantially depending on the urgency of the trip made. At the low end, the mean VTTS for a traveler who wants to make extra stops and still arrive on time is approximately 10% higher than that for an ordinary trip. At the high end, a traveler running late for an appointment shows a mean VTTS that is approximately 300% higher than that for an ordinary trip. These estimates vary widely over the population of travelers. In light of these variations, the value of an uncongested travel alternative (such as MLs) is examined and found to be greatly undervalued if using typical VTTS estimates.     

Surface prediction and control algorithms for anti-lock brake system

Anti-lock brake system (ABS) has been designed to achieve maximum deceleration by preventing the wheels from locking. The friction coefficient between tyre and road is a nonlinear function of slip ratio and varies for different road surfaces. In this paper, methods have been developed to predict these different surfaces and accordingly control the wheel slip to achieve maximum friction coefficient for different road surfaces. The surface prediction and control methods are based on a half car model to simulate high speed braking performance. The prediction methods have been compared with the results available in the literature. The results show the advantage of ABS with surface prediction as compared to ABS without proper surface identification. Finally, the performance of the controller developed in this paper has been compared with four different ABS control algorithms reported in the literature. The accuracy of prediction by the proposed methods is very high with error in prediction in a range of 0.17-2.4%. The stopping distance is reduced by more than 3% as a result of prediction for all surfaces.