Headway

About: Headway is a research topic. Over the lifetime, 3266 publications have been published within this topic receiving 50121 citations. The topic is also known as: Train headway.

Enhanced intelligent driver model to access the impact of driving strategies on traffic capacity

Abstract: With an increasing number of vehicles equipped with adaptive cruise control (ACC), the impact of such vehicles on the collective dynamics of traffic flow becomes relevant. By means of simulation, we investigate the influence of variable percentages of ACC vehicles on traffic flow characteristics. For simulating the ACC vehicles, we propose a new car-following model that also serves as the basis of an ACC implementation in real cars. The model is based on the intelligent driver model (IDM) and inherits its intuitive behavioural parameters: desired velocity, acceleration, comfortable deceleration and desired minimum time headway. It eliminates, however, the sometimes unrealistic behaviour of the IDM in cut-in situations with ensuing small gaps that regularly are caused by lane changes of other vehicles in dense or congested traffic. We simulate the influence of different ACC strategies on the maximum capacity before breakdown and the (dynamic) bottleneck capacity after breakdown. With a suitable strategy, we find sensitivities of the order of 0.3, i.e. 1 per cent more ACC vehicles will lead to an increase in the capacities by about 0.3 per cent. This sensitivity multiplies when considering travel times at actual breakdowns.

A Comparision of Spacing and Headway Control Laws for Automatically Controlled Vehicles1

Abstract: SUMMARY This paper investigates two different longitudinal control policies for automatically controlled vehicles. One is based on maintaining a constant spacing between the vehicles while the other is based upon maintaining a constant headway (or time) between successive vehicles. To avoid collisions in the platoon, controllers have to be designed to ensure string stability, i.e the spacing errors should not get amplified as they propagate upstream from vehicle to vehicle. A measure of string stability is introduced and a systematic method of designing constant spacing controllers which guarantee string stability is presented. The constant headway policy does not require inter-vehicle communication to assure string stablity. Also, since inter-vehicle communication is not required it can be used in systems with mixed automated-nonautomated vehicles, e.g for AICC (Autonomous Intelligent Cruise Control). It is shown in this paper that for all the autonomous headway control laws, the desired control torques ...

Public Transit Planning and Operation: Theory, Modeling and Practice

Abstract: Preface, Introduction to Transit Service Planning, Data Requirements and Collection Frequency and Headway Determination, Timetable Development, Advanced Timetables I: Maximum Passenger Load, Advanced Timetables II: Maximum Synchronization, Vehicle Scheduling I: Fixed Schedules, Vehicle Scheduling II: Variable Schedules, Vehicle-type and Size Considerations in Vehicle Scheduling, Scheduling, Passenger Demand, Route Choice and Assignment, Service Design and Connectivity, Network (Routes) Design, Designing Short-turn trips, Smart Shuttle and Feeder Service, Service Reliability and control, Future Developments in Transit Operations, Answers to Exercises, Index

A headway-based approach to eliminate bus bunching: Systematic analysis and comparisons

Abstract: Bus schedules cannot be easily maintained on busy lines with short headways: experience shows that buses offering this type of service usually arrive irregularly at their stops, often in bunches. Although transit agencies build slack into their schedules to alleviate this problem - if necessary holding buses at control points to stay on schedule - their attempts often fail because practical amounts of slack cannot prevent large localized disruptions from spreading system-wide. This paper systematically analyzes an adaptive control scheme to mitigate this problem. The proposed scheme dynamically determines bus holding times at a route's control points based on real-time headway information. The method requires less slack than the conventional, schedule-based approach to produce headways within a given tolerance. This allows buses to travel faster than with the conventional approach, reducing in-vehicle passenger delay and increasing bus productivity.