Forums Forums Traffic Signals Intergreen Limit Values

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  • #3299
    Chris Pearson
    Participant

    Given the discussion about calculated intergreens etc, has there been any case law involving shorter intergreens?

    The only reason I ask this question that the strict rule of law says:

    “Vehicular traffic proceeding beyond a stop line in accordance with paragraph (1) to (4) must proceed with due regard to the safety of other road users and subject to any direction given by a constable in uniform, a traffic officer in uniform or a traffic warden or to any other applicable prohibition or restriction”

    So while I accept that we have a duty to ensure that our junctions are as safe as possible, the rule of law *appears* to put the onus on the driver as to safe behaviour so far as is possible – obviously all prevailing site conditions considered.

    #3298
    Anonymous
    Inactive

    I’d generally always have the same value as the calculated intergreen. The only exception to this rule I can think of is if I’ve specified an intergreen higher than calculated, such as on a high speed MOVA approach.

    #3265
    dhulson
    Participant

    I usually set the limit values to the value suggested by the geometry as whilst I might increase an intergreen based on site observations I am very unlikely to want to reduce one to below the value that national standards recommend.

    #3262
    Anonymous
    Inactive

    Assuming you have calculated your intergreens in accordance with standards (local or national) why would you set a limit lower than you have calculated and what would be the reasoning (and defense) for using a lower (safety) timing?

    #3257
    ianwallis
    Participant

    I usually leave at the default of 5s unless there is something I specifically want to protect, for example a min intergreen on a shuttle bridge. Generally though I agree with Chris – being unnecessarilly restrictive usually results in having to procure new PROMs with it’s attendant costs and delays in making the changes.

    #3255
    daveo
    Participant

    We usually set them 1 or 2 sec below specified

    #3251
    David Hughes
    Participant

    We tend to have an intergreen limit 1s below the specified intergreen

    #3250
    Chris Pearson
    Participant

    I tend to allow everything to go down a couple of seconds in the first instance, to allow for a bit of on-site adjustment if required.

    I dont see the point in being unduly restrictive in 2500’s as the way I see it, it is the designer and the maintaining engineers responsibility to make sure that everything is safe. By all means have default values that will take over if the RAM is cleared for whatever reason, but reducing the options available on commissioning or if things change a bit in the future just makes for extra work if you have chosen to be a little over-cautious when calculating the intergreens and setting limit values.

    But then again, Im also not averse to setting intergreen levels lower than 5s either, especially when there is no clear reason to by virtue of geometry.

    #1053
    David Parkin
    Participant

    Could I ask for a pole of how people use the Intergreen Limit Value in the controller specification forms. I know some engineers will allow the limit value (Form IX on the MCH1827B forms) to be less than the actual intergreen value (Form VIII), but some engineers will always ensure the limit value is the same as the intergreen.

    Please let me know what you do.
    Thanks

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