bus interval and schedule

February 14, 2012

Waiting for the bus on Robson, Broadway, or 41st, what is important to you: that the bus is “on time”, or that it arrives in the expected frequency interval?

bus operated on schedule

Ensuring scheduled runs, under unreliable traffic condition, can request significant leeway in the layover to absorb any delay at the bus terminus, what can lead to the picture below, which looks like as a poor utilization of bus resource:

buses laying over at Davie and Denman

Furthermore, to respect the schedule along long route, some timing point are necessary to allow adherence to it and to avoid bus bunching.

time point along route 41 (UBC-Joyce Station)

Whether those time points, either

  • doesn’t provide enough leeway, and they become useless (the bus is still late on them)
  • or provide too much lack- what is not only inefficient, but is frustrating for enroute rider

Normally you could expect that the buses are fairly distributed along the route – to provide a regular interval as built in the schedule, but the reality can be pretty much different:

snapshot of buses on route 41 on thursday Feb 9, 2012, around 2pm

…and bus bunching is still a reality of life:

A zoom on he route 41: 5 east bound bus are spotted here, 3 in the same block, 2 in the 9 others block... Is the bus driver the only one not knowing he is stepping on the back of another bus?

It must be a better way to operate a frequent bus route. When the frequency is supposed to be less than 10mn, do people really care about bus schedule?

bus operated on interval

That is typically, the way the buses in Paris inner city operate: no schedule at all is provided to the customer, just a frequency map. That gives lot of leeway for the operator to operate its bus according to the condition of the day:

  • The operator bus schedule can vary according the day of the week, and week of the year
  • The operator bus schedule can vary according presence of roadwork, and weather forecast

All that is used by the operator to plan the number of buses to operate on a route at a certain time of a certain day, and is not exposed to the customer, which just care about frequency – and generally understand that bus can’t move faster than traffic (unless bus lanes and other road priorities measure).

To avoid bus bunching, the Parisian RATP operator uses the Global positioning system to inform the bus drivers about spacing with buses in front and behind. The driver is supposed to regulate itself to maintain an optimal interval (so is not asked to adhere to a schedule per sei) [1]

That makes obsolete the time point mechanism, and eventually is from nature to

  • increase the average bus speed
  • lower the fleet requirement

The operation on an “interval” is not applied in the Paris suburbs, where bus operates on “schedule” but the operation on “interval” could apriori make sense for high frequency route, like the illustrated route 41…even in Vancouver


[1] Research result digest, October 1998, Transit Cooperative Research Program

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3 Responses to “bus interval and schedule”

  1. The Other David Says:

    As a user of the 130, where there seems to be no “regular” interval.

    Saturday
    3:56pm 4:03pm 4:15pm 4:18pm 4:26pm 4:32pm 4:45pm 4:47pm 4:55 pm

    2 minutes, or 13 minutes… I’d prefer they be accurate.

    Weekdays:
    6:31pm 6:37pm 6:46pm 7:01pm 7:22pm

    If you miss the 7:01, you may as well walk to Brentwood, it’s quicker.

    (The 130 has 3 or 4 northern terminii.. (Hastings, Kooteney Loop, Phibbs, Cap U).. which probably explains the asymmetric schedule)

    re The Real Time Map… the buses don’t constantly report their location… each bus’s location can be up to 2 minutes out-of-date. and they don’t report at the same time… So bunching on the map may not represent the actual relative locations of the buses.

    (That said, I should look up a rant I posted years ago about trying to catch the 99 at Broadway and Granville (not a timing point… 15 minute intervals (to Brentwood).. and often early and late)

  2. Voony Says:

    Other David, good point on the real time map – that said, I think the essence of the post is still right (I occasionally see bus bunching, and 410 is pretty prone to it). For an “interval” spacing operation, the buses location could need to be updated more frequently than every 2mn (I guess it is done like it to not jam the Translink communication system, but it could be probably modified for some route if needed)

    On the 130 odd schedule, it eventually demonstrates the limit of research of operating efficiency: here the schedule is probably designed like it to be efficient from the operator viewpoint, but it is not at all from the customer viewpoint…

    When the Swisses have introduced their clockfaced system (what eventually even include slowing down some trains to make “perfect” connection), it had a price in efficiency to be paid…but the system has been so customer friendly, that the general outcome was largely positive…


  3. [...] [3] See some explanation in this post [...]


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