Assist and automation technologies provide automated lateral and longitudinal control of the BRT vehicle, either to assist the driver in safely operating the vehicle or to directly control the vehicle. The different automation technologies are described below:
- Collision Warning and Avoidance
Collision warning alerts the vehicle driver to the presence of pedestrians or other obstacles, while collision avoidance directly controls the BRT vehicle to avoid hitting these obstructions. Collision warning and avoidance technologies comprise forward, rear or side impacts, or 360-degree system integration. Driver notification devices and infrared, video or other sensors are required for both technologies, while collision avoidance requires the added provision of automated controls within the vehicle. Although collision warning systems have some limited commercial availability, collision avoidance systems are still being tested and are not yet on the market.
- Precision Docking
Precision docking uses either magnetic or optical-based methods to assist BRT drivers in lateral and longitudinal positioning of vehicles at stops or stations. These technologies require magnets or paint markings to be installed on or in the pavement, vehicle-based sensors to detect the markings, and connections to the steering mechanism. The Civis vehicle used by the Las Vegas MAX BRT system is equipped with an optical guidance system that enables precision docking at station platforms. The availability of these systems is currently limited to international suppliers as an additional option for new vehicle purchases. Commercial availability from U.S. suppliers as an add-on option is expected in the next two to five years.
- Vehicle Guidance
These systems use a variety of technologies to guide BRT vehicles on running ways. Also known as "lane assist technologies," automated guidance systems allow BRT vehicles to operate safely at sustained speeds on limited right-of-way. There are three primary vehicle guidance technologies: magnetic, optical and GPS (global positioning systems). As with precision docking, the magnetic and optical technologies require magnets or paint markings every few feet along the roadway, vehicle-based sensors and a steering actuator. GPS methods rely on wireless communications, highly accurate GPS-based maps, on-board software and a steering actuator to guide the bus. Magnetic, optical and GPS guidance methods are comparable in terms of cost. However, magnetic and optical systems appear to be more reliable than GPS, which is vulnerable to wireless signal failure due to uneven terrain or other natural and man-made obstructions.
Vehicle Prioritization Technologies
This class of technology enhances operational efficacy through the provision of preference or priority to the BRT vehicle. By reducing the traffic signal delay experienced by the BRT vehicle, these technologies can achieve increased operating speeds, decreased travel times and greater schedule or headway adherence. Signal retiming, synchronization, phasing and transit signal priority (TSP) help BRT systems to minimize delays caused by having to stop at controlled intersections. Access control provides BRT vehicles with unencumbered entrance to and exit from dedicated running ways and/or stations.
Ongoing research by NBRTI, the University of California PATH, and others has focused on:
- Developing recommendations on TSP warrants and updates to the Manual of Uniform Traffic Control Devices to address traffic engineers' concerns about TSP.
- Developing and demonstrating operational standards such as the NTCIP (National Transportation Communications for ITS Protocol) Standard 1211, adopted in December 2005, which defines a method of granting priority to one signal while maintaining coordination with adjacent intersections.
- Assessing the applicability of intermittent bus lanes (IBL) in the United States. Developed by Prof. Jose Viegas and others at the Instituto Superior Tecnico in Lisbon, Portugal, the concept involves changing the status of a regular traffic lane to buses only when a bus is approaching. Advanced technology is required to monitor bus location in real-time, provide information to drivers via variable lane signage and lighting (Viegas et al, 2007).