Advanced stop line
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An advanced stop line (ASL), 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.
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[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] ASLs for cyclists
Advance stop lines for cyclists are generally used in conjunction with some form of cycle-lane for filtering cycle traffic. In fact, the traffic regulations in some countries (eg UK and Ireland) may require a cycle-lane so as to provide the cyclists with a legal way of bypassing the first stop line. This arrangement theoretically allows cyclists to play to their strengths by regularising the practice of filtering to the top of queuing traffic during the red phase at traffic lights. Cyclists turning to the offside (eg Right in UK/Irl Left in USA etc) are able to take up a proper turning position. Straight-on cyclists can adopt and maintain a prominent position for transiting the junction safely within the main traffic stream. An ASL will also help reduce the exposure of such cyclists at junctions with nearside (eg Left in UK/Irl Right in USA etc) filter lights by providing a place for cyclists to wait while traffic passes on the inside. A similar consideration arises where a free turn to the nearside is permitted (so-called right-turn-on-red in the US).
[edit] ASLs: Safety issues
Based on Danish research, it is argued that an ASL should be arranged with the stop line for motorised traffic 5m back from the main traffic signal. The reasoning is that this puts the cyclists clearly into the view of HGV (heavy goods vehicles) drivers, who have a blind spot up to 4m directly in front of the cab. According to an OECD review, ASLs are also advocated as way of improving pedestrian safety at crossings by increasing the separation between crossing pedestrians and waiting motor vehicles.[1]
Although waiting cyclists might be safer out in front of HGVs, concerns have been expressed about the use of nearside (kerbside) cycle lanes to approach such intersections; specifically that these feeder lanes may encourage some cyclists to "creep up" on the inside of turning HGVs. Collisions with turning HGVs are strongly associated with a high risk of death and serious injury[2]. For instance Cyclecraft by John Franklin is considered to be a standard text on safe cycling for UK and Irish cyclists. In the 1997 edition, Franklin's advice for cyclists is that they should only use such feeder lanes if the traffic signal is red. If the signal is green, cyclists are advised that the best way to minimise danger may be to stay within the main traffic stream. If the lights change while the cyclist is still approaching, the advice is to negotiate their way back into the main traffic stream if possible. Advice produced by RoSPA regarding cyclists and lorries cautions cyclists that even though a junction has ASLs it may be better to hang back if there is a lorry present.[2]
A leaflet[3] 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.
[edit] Jurisdictions which employ advance stop lines
- Canada
- Vancouver, BC
- Montreal, PQ
- The Netherlands
- Various cities
- UK - nationwide
- US
- Portland, OR (limited)
- New York, NY
- Australia
- Victoria
[edit] External links
- Do Advanced Stop Lines Work? London Cycling Campaign group evaluates ASL performance in Westminster, UK
[edit] Notes
- ^ Safety of Vulnerable Road Users, OECD, 1997
- ^ a b Cyclists And Lorries Royal Society for the Prevention of Accidents February 2006
- ^ Advanced stop lines for cyclists. UK Department for Transport.
