Advanced stop line

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An advanced stop line (ASL), bike box (Canada), or cycle reservoir (UK) is a type of road marking used at signalised road junctions. The intent is to allow certain types of vehicle a head start when the traffic signal changes from red to green.

1 Description of use
2 Effectiveness
3 Jurisdictions which employ advance stop lines
4 External links
5 Notes

[edit] Description of use

Most commonly associated with bicycle traffic they may also be provided for buses and motorcycles. Essentially there are two parallel stop lines at the intersection, the first one at which all traffic, except that for which the facility is provided, must stop, and an additional one after this, which only the specified vehicles may proceed to. The area between the stop lines is the "reservoir" or "box". Signage may be required to inform road users as to the meaning of the extra stop line. In some situations, a separate set of traffic signals may be provided for bus or bicycle traffic. However, in most cases all vehicles use the same signals.

[edit] Effectiveness

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It is claimed that employing advanced stop lines can be an effective method of separating vulnerable road users, which will thereby improve safety. This separation is achieved by taking advantage of the fact that non-motorised traffic accelerates more rapidly than motorised traffic. An advanced stop line can allow vulnerable road users to clear the intersection before motorized vehicles enter.

Some jurisdictions may allow turning vehicles to "break" lights - so called right-turn-on-reds (for drive-on-the-right countries). To be effective in such jurisdictions, it is argued that there must be a ban on such motor vehicle turning movements during the red signal phase.

A leaflet^[1] produced by the UK Department for Transport notes:

ASLs have been used successfully at sites with motor vehicle flows up to 1000 vehicles per hour, and with two lane approaches. In Bristol they have been used on the approach to a signalised roundabout. Success will depend on cars not blocking the cycle lane or encroaching on the reservoir, and on signal timings which ensure that cyclists are not frequently stopped.