In 2005 Transport for London purchased one of the worlds largest real-time passenger information and fleet management systems in a project valued at 117M with the objectives of equipping 8000 vehicles with GPS tracking and installing500 passenger information signs. The option to expand the system to deploy priority at traffic signals for buses was made in April 2006 which requires up to 3200 sets of signals to be upgraded. With such a large scale deployment a number of useful tools and methods have been developed to minimise waste and improve efficiency. In view of the increasing competition for road space, an important tool for improving bus services is bus priority at traffic signals. This can increase buses share of the time available at signalled junctions, reduce delays to buses at junctions and potentially provide greater regularity in bus schedules. Bus priority in London was developed by the use of selective vehicle detection to give buses priority extensions and recalls at traffic signals. Previous systems have used transponders fitted to the buses linked to antennas buried in the carriageway (bus loops) and roadside beacons communicating with on-bus transponders via a short microwave link. Currently, 45% of the 3200 signalled junctions are fitted with one or other of these types of equipment. Bus priority at signals has contributed to the 38% increase in bus patronage since 1999. A description of the IBUS system is provided. It is fitted to 8000 buses (scope for 16000); and all 3200 traffic signals are to be fitted. Virtual detectors are used, avoiding on-street hardware. RTIG standard radio link from buses to signals adapted to allow ACK from signals to bus. Provision for messages from signals to buses is a future option. A bus processor unit provides an interface to signals. The network of bus processors is connected to a bus priority instation. There are extensive data collection and monitoring facilities in the iBUS central system allowing greatly improved system management for bus priority. The system supports a short range radio link for message transmission to traffic signals, giving up to 4 notifications for an approaching bus. The location of the virtual bus detector in each approach to the junction is dependent mainly on the extension requirements. Bus priority is currently awarded through green extensions and green recalls. It has been shown that green extensions are most sensitive to detector siting and that optimal siting for green extensions is also appropriate for green recalls. Optimum detector distances have been calculated for different bus speeds on different categories of approach. A different method is needed where there is a bus stop close to the signals and iBUS contains special procedures for triggering the priority request at bus stops in order to obtain the maximum benefit to the buses. The benefits from bus priority at signals are well understood and documented in London as a result of previous experience over a period of 20 years. The analysis used in the development of iBUS indicated that total costs over the 15 year expected lifetime of the system, including capital and operational costs would be 39M and that benefits would be 147M, giving a Net Financial Effect of 108M. The magnitude and timescale of the roll-out (800 junctions/year over four years) plus the need to work in harmony with existing complex technical and organisational structures calls for a high degree of organisation. For the covering abstract see ITRD E137145.
Abstract