Summary

i. Problem Statement

The coordination of the movement of trains and motor vehicle traffic at both grade crossings and rail/roadway intersections can be difficult. Although different railroad grade crossing control products are available, the most challenging limitation to traditional grade crossing systems is the inability to deliver consistent warning times with varying train speeds and station stops (particularly the nearside stops). As the results, rail-roadway crossings often generate conflicts and congestions for motorist traffic and sometimes delays to trains.

ii. Research Plan

This project will investigate the interaction and conflicts between urban/suburban rail and associated cross traffic and to develop integrated and practical solutions for minimizing the delays to motor vehicle traffic while improving schedule adherence for rail operation. The proposed approaches to the crossing problems are two folds: (1) Practical means for deliver consistent detection time including effective sensing approaches and means for predicting Time-to-Arrival at the grade crossing and (2) Adaptive signal control strategies using consistent detection time and integrated with the existing grade crossing control technologies. This project plans to conduct field testing of the system concepts and algorithms developed under this project with an aim for deployment. This is a two year project.

Methodologies

The proposed research will deal with the grade crossing problems using a systems approach with a goal of field deployment. The study will take the following approaches:

(i) At the systems level, the proposed studies will analyze the interaction between rail and traffic and assess the impacts of different designs, operation, and technological options.

Case studies will be conducted using actual grade crossing designs along San Diego light rail. This proposal will utilize the Paramics simulation model to simulate specific designs and detection and signal control strategies.

(ii) Develop detection approaches to minimize gate or intersection closure times

The critical technical difficulty of existing grade crossing systems is primarily due to the inaccuracy of estimating the time-to-Arrival (TTA) to the crossing. Both the approaching circuits and advance inductive loops can only inform the grade crossing system of the approaching train with a constant TTA and there is no detection means for determining the duration of station boarding/alighting. Based on a broad literature review of state-of-the-art technologies and concepts, an integrated design of an advanced grade crossing signaling system will be proposed. Two elements are to be studied in detail. We propose to develop an accurate and consistent detection time, which will include detection means for acquiring train's position and velocity before approaching the intersection and a prediction algorithm that will give accurate TTA predictions with a prescribed lead time. At least two approaches will be evaluated with a strong consideration of the practicality and cost effectiveness of deployment. The first approach is to use vehicle-borne continuous positioning method and vehicle-to-roadside communication system. Most urban rail operators (such as Samtrans, San Diego and VTA) are planning to install GPS-based AVL systems for train movement monitoring and management. The approach of using a GPS-based AVL is consistent with the train operators plans and therefore can be very cost effective. The second approach is to use advanced approaching detection such as a Honeywell grade crossing scanner combined with failsafe radio frequency technology. Using the continuous or advanced train location information, velocity, and possibly door open/close status in conjunction with the historical travel data, a prediction algorithm will be developed to provide accurate prediction information.

(iii) Develop adaptive preemption and priority treatment strategies in order to reduce the impact of cross traffic

The second critical technology is the preemption and priority treatment algorithm. Upon receiving the train detection notification and its TTA, the preemption and priority algorithm actuates the signals for commanding pedestrians and motors vehicles to complete the right of way transfer, queue clearance and separation. We propose to develop an advanced preemption and priority algorithm that will perform the preemption/priority sequence by adequate calculating the time window a train will need to pass the crossing, accurately placing the time window within a traffic cycle and distributing this time window to multiple phases prior and after impacted.

(iv) Develop an integrated application

Based on the knowledge of both railroad and traffic systems, the proposal team will take an integrated approach to implement the advanced detection methods, TTA prediction algorithm, and adaptive preemption and priority treatment algorithm by developing a prototype of the adaptive preemption/priority system. This will be integrated with the existing grade crossing traffic control devices.