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Advance Stop Lines at signalled junctions - comments for a new advice note

edited October 2008 in General
Local Transport Projects (LTP) Ltd., have been asked by Cycling England (a DfT funded organisation) to produce an advice note regarding the installation of Advance Stop Lines (ASL's) for cyclists at traffic signal controlled junctions. LTP would appreciate any feedback from Forum members regarding their experience of ASL's - anything relating to the design, operation, results, impacts on signal sites (both positive and negative) and innovative practices. The note is intended to advise practioners desiging new ASL sites and therefore any feedback from Forum members would be extremely beneficial. The comments from traffic signal specialists will also be invaluable for this advice note.
Please post any replies to this Forum and if you need to contact LTP, the contact there is Andy Mayo
www.local-transport-projects.co.uk
Andy.Mayo@local-transport-projects.co.uk
Tel (01482) 679911

Comments

  • A key issue we have encountered when ASLs are retrospectively applied is the need to consider detection layouts, particularly with AGD and stop-line loop arrangements. It may not occur in better co-ordinated authorities, but sometimes our planners combine an ASL with some other work on a corridor and don't consult the traffic signal staff.
  • 1) Signal intergreen values - There seems to be no definitive rule of which stop line(s) to measure from for the stopping or starting traffic?
    2) ASL size - 5m seems excessive when combined with new TAL1/06 advice of min 3m between stop line & studs - or should the 3m be reduced in these circumstances?
    3) Should there be detection in ASL? eg for vehicle stopped in ASL beyond traditional stop line loop position?
    4) With Mova - should site validation be getting signals to change as vehicles pass 1st stop line or that at signal pole?
    5) ASL across all lanes or partial?

    Above all the regular retrospective (in our experience UTC always being unaware) introduction of ASLs needs to be addressed and the effects on the above issues considered.
  • Since this was originally posted LTN 2/08 “Cycling Infrastructure” has been issued by Dft
    http://www.dft.gov.uk/pgr/roads/tpm/ltnotes/ltn208.pdf

    Anyone wishing to comment might want to familiarise themselves with the new LTN.

    Re Phil’s comments

    Signal intergreen values ~ As traffic is “supposed” to stop @ the first stop line shouldn’t I/G’s be from there

    ASL Size ~ LTN 2/08 9.4.4 Suggests a minimum of 4 M and Maximum of 5M

    Detection In ASL ~ Hmmm.. I have never done so but can see where your coming from assuming that approach detection is set with correct extension to clear “second” stop line probably not. More to the point on a MOVA job where would you have the “stop line” loop??

    Site Validation for MOVA ~ Perhaps Dr Spence can give us his opinion on this but I would suggest that as drivers are supposed to stop at the first stop line…. 9so long as the I/G is correct

    ASL across full width. I have NEVER seen the point of ASL across full width when a R/T is NOT permitted (and some even show this across three lane approaches.

    The LTN also points out that ‘multiple’ “lead in” lanes on same approach requires authorisation.

    Any thoughts re detection in “lead in” lanes??


    Tony Sharp
  • edited November 2008
    In Blackburn we have a couple of cycle lanes with D loops in them - which work brilliantly (not) with the carbon fibre/alloy bike frames we have nowadays.

    I'm about to start making use of the magnetometer detectors from Clearview - so we shall see just how well they work with modern cyclists.

    And we're not known for being massive fans of cycling in this country. Has anyone actually monitored the use of ASL's by cyclists and whether they are actually used at all in the way that they are intended?

    EDIT: My colleagues and I have been looking through LTN2 /98 and its more of a compendium of How Not To Do Traffic Engineering than anything else. I would hope that Figure 9.4 was swiftly removed from street - in fact I have to wonder why DfT even published the picture in the first place! Another one is Figure 7.2 which invalidates the double yellow lines - and thats given as a good example? Come on!
  • I agree re the suggestion that 5 metres max depth is excessive. This measurement is applied as a standard in Edinburgh and I have queried the use of such a distance in a city where under 1% of daily commuters are cyclists.
    Also I've come across certain sites where the lagging stop line can be >7 metres from the nearest primary signal - some drivers tend to 'stop in the gap', between the sig pole and the lagging stop line, when the sigs change to leaving amber. Also is there any Police enforcement (covering unlawful ASL encroachment by drivers) applied in England? It certainly doesn't exist in Edinburgh. Hence there has been an ongoing debate re providing this facility at all.
  • While not the biggest fan of ASLs I would suggest that if they're going to be installed then they should be fit for purpose. If a cyclist is to approach on a nearside cycle lane and then position himself to turn right in full visibility of cars waiting at the stopline he needs to have a reasonable amount of room. As a cyclist I find 3m ASLs much too short to do this easily whereas a 4m or 5m gives me that manouvreing space. Bear in mind that your average touring cycle is about 2m long.
  • On this issue, I'm struggling to find some advice / guidance relating to the design and installation of loops to detect cycles. Can anyone direct to me the relevant doc' (s). Thanks
  • Just revisited this for my own benefit and decided to add a further thought.

    The junction I am working on has MVD detection so the stopline loop is only used as a backup in case of failure of the MVD or at times of stationary traffic due to an incident etc. (I only use them to demand a stage not extend it due to the chance of damage and the time taken to repair). Similarly at MOVA junctions, the stopline loop is only used where traffic can enter the lane between the X loop and the stopline (unless you use it as an alt-down) and can be omitted from the design anyway in some cases. With this in mind I am proposing to install stopline loops in each lane 4m long with 2m each side of the stopline. This should cater for most situations bearing in mind that should no demand be detected by the MVD vehicles at a "stuck" red will creep forwards and eventually be on the loop even if they've previously stopped short. If they're sensitive enough I usually find they detect most vehicles without the need for any special detection.
  • Care should be taken with infra red and/or video detection. It is hit and miss whether you can get an infra red detector to reliably detect for both zones. A N/S post mounted infra red detector will not be 100% effective on the vehicle stopline alone, if you compromise and set the input as latching then you have the inconvenience of false calls by pedestrians. Video detection can cover both zones but usually cant fit the entire detect area onto it's field of view. No resolutions for this, so I'd suggest either 1 sensitive latching loop at the vehicle stopline (for both vehicles and cycles) or 1 loop for each detect zone. We don't tend to have any problem in London as vehicles use the ASL as a matter of course. I've actually been abused by a Taxi driver for having the audacity to stop at the correct stopline!
  • edited January 2010
    With video stopline detection I always set them up as call/cancel detectors. Pedestrians invariably pass through the area without loitering so this overcomes any issues of false calling.
  • MOVA was mentioned above. In my own opinion, stop line loops should ALWAYS be provided at all MOVA sites (except perhaps motorway slips) as the low sensitivity MOVA loops will always miss a bicycle and often a motorcycle. I specify the 'chevron' style detector to be placed in reverse direction, i.e. with the end nearest the kerb side furthest from the stop line, because the cyclist often heads towards the kerb at the stop line and can still be missed with the conventional 'chevron' loop layout, whilst further from the stop line he is more likely to ride over the loop. Also stop line detectors need high sensitivity to ensure MOVA demands are entered by all unusual vehicles/bicycles.
  • Steve,

    Regarding the cycle loops. See my discussion on page 2 'loop layout diagrams'
  • My view is 5m resevoirs should always be used as 4m leaves the potential for cyclists to be in the advanced area on the nearside and still be invisible to lorry drivers in certain types of vehicles waiting at the stop line. This has raised a few issues in London though as our specifcation is for 3m stopline to studs and 500m primary pole to studs thus creating 7.5m from first stopline to primary signal. However to re-iterate my personal opinionon this, 4m resevoirs can't be guaranteed to make cyclists visble to lorry drivers waiting to turn left.
  • Additional comment re: which stop-line is legal. TSRGD is quite clear in stating that eith stop-line can be used. Therefore the stance taken in London is to measure intergreens in a pessimistic manner to allow for the worst case scenario. This was not covered in the original TRL report, as TSRGD 1994 was current at the time, and its distinction was decidedly wooly.
  • edited August 2011
    [quote]
    'I specify the 'chevron' style detector to be placed in reverse direction, i.e. with the end nearest the kerb side furthest from the stop line, because the cyclist often heads towards the kerb at the stop line and can still be missed with the conventional 'chevron' loop layout, whilst further from the stop line he is more likely to ride over the loop.'
    [/quote]

    We tend to specify stopline loops cut to 0.3m from the kerb to avoid cycles been missed although we do get some complaints from slot cutters as it is a little harder for them.
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