FLARE: A program for estimating the usage of under-utilised flares at traffic signal junctions

摘要

A significant proportion of traffic signal junctions within the U.K. contain a short lane(s) or 'flare' on one or more approach. Many of these flares do not share a common movement with the adjacent full lane and will therefore be under-utilised. This under-utilisation occurs as a result either of queueing in the adjacent full lane, blocking entry to the flare; or of overflow queueing from the flare, creating gaps in the queue in the adjacent lane. In both cases the under-utilisation must be taken account of when estimating a value of flare usage per cycle for inclusion in OSCADY (Card Type 6) or LIN-SIG (Link Type B). Failure to do so, or to do so accurately, can result in a significant under- or over-estimate of lane group capacity. For instance, with a relatively short cycle time of 60 seconds, and an error in the estimate of flare usage of up to 3 pcu per cycle for a single-lane flare, capacity may be under- or over-estimated by up to 180 pcu/h. This could amount to 10 per cent or more of lane group capacity. FLARE is a computer program for estimating the usage of under-utilised flares. It allows for under-utilisation by using simulation techniques to model the arrival and departure of individual vehicles in the flare and adjacent lane. This simulation is based on signal timings, traffic flows and saturation flows provided by the user; most of this information can be taken direct from OSCADY or LINSIG.