Observational Analysis of Tram Delays in Inner Melbourne

A research paper presented at the Australasian Transport Research Forum, September 2007.

Summary

Think Tram is a programme, run in partnership between Melbourne’s private tram operator Yarra Trams and agencies of the Victorian Government, to improve running times for trams in Melbourne. Outcomes to date for Think Tram have been poorer than those seen in similar tram priority programmes in other cities around the world. In part this is due to community opposition to specific measures proposed, but concerns have also arisen that specific Think Tram proposals have been poorly targeted and are not sufficiently effective in reducing travel times. Comparisons between the typical measures implemented in Think Tram projects to date and those implemented in ‘best practice’ cities elsewhere tend to bear out this criticism.

This paper seeks to provide a positive contribution to the tram-priority debate by studying in some detail the factors contributing to the bulk of delays on one typical inner Melbourne tram route. This research has been motivated by anecdotal observations that Melbourne trams spend greater lengths of time waiting at red lights compared to trams elsewhere, and that this is a signficant factor in slow tram travel in Melbourne. Measurements have been taken, over a five-month period, of morning and evening peak travel times on the route in question and of the accumulated ‘dead time’, so defined as to isolate the effect of lack of traffic priority from other sources of delay such as the frequency of stops, or heavy passenger loadings.

The study provides significant evidence for the following conclusions in regard to the study route:

‘Dead time’ is a significant predictor of the variation in peak hour travel time.
The most significant factor contributing to dead time is adverse traffic signals, with other significant factors being traffic congestion, fouling of tracks, tram congestion and operational events.
Within the City of Melbourne boundary, where trams are not subject to significant traffic congestion, dead time accounts on average for one-third of overall travel time, with a mean of nearly 6.5 minutes out of 19 minutes.
Outside the City of Melbourne, dead time accounts on average for about 13% of overall travel time, with a mean of nearly 2 minutes out of 14-15 minutes. Traffic congestion does not always contribute to the dead time, but when present its typical contribution is in the order of one minute.
The elimination of dead time would improve average travel speeds for trams in peak hour by around 50% within the City of Melbourne and by around 20% further north.
Lack of punctuality is an indirect contributor to delays, as a consequence of overcrowding.
The presence of a clearway can avoid additional dead time due to traffic congestion of up to 60 seconds on a 2km stretch of mixed running, though this effect is not consistently observed. The effect is smaller than the additional dead time contributed by adverse traffic signals.
The mean dead time observed off-peak is around 80% of that observed at peak times, except in the late evening. There is little qualitative difference in the dead time characteristics between peak and off-peak times.

Our primary recommendation is that tram priority measures must concentrate primarily on expediting the movement of trams through signalised intersections, in similar vein to the scheme employed in Zurich, and not simply through the phase-insertion approach already in place. Particular effort needs to be directed toward signal priority within the City of Melbourne boundary.

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