Urban trains and trams should be limited to 20mph according to TAC theory

The Transport Accident Commission (Victoria Australia) speed propaganda program is supported by calculations of reaction and braking distances.  One of their advertisements illustrates a pedestrian being struck by a driver traveling at 65km/hr but having not being affected if the car had been traveling at 60km/hr (relying on 25m reaction being 1.5s and 20m braking).  Conveniently for their argument the pedestrian was 45m away when seen.  That’s the gist of the campaign.

Getting hit by a train or tram is no less damaging that by a car, so presumably they should travel according to the same requirements.  Allowing a railed vehicle deceleration of 1m/s, the same reaction time, ignoring grade and train braking system delay, the distance would be given by D=RV + VV/2A (V=velocity, R=reaction time, A=deceleration).

Applying the 45m theory which is apparently vital with regard to cars seeing pedestrians: 45=1.5V+VV/2.

This gives a safe speed for trams and trains of V=8.1m/s or 30km/hr (~20m/hr).*

Trains and trams in Victoria routinely travel a lot faster than 30km/hr thus severely endangering pedestrians according to the TAC’s theory.  So where is the campaign to get them to slow down?  Good for the goose but not the gander?

RIMG0919  RIMG0666

*Actually it will be generally lower due to brake delay and more so in the case of downgrade.  Alternatively under emergency braking (e.g. 2.8m/s) it will be greater, although at the risk of wheel and track damage, with the allowable speed increasing to 12m/s or about 43km/hr (27m/hr).


About John Culvenor

Hi, Thank you for taking a look at this blog. I work in engineering, ergonomics, creativity, design, training, etc. Often this is about helping solve legal puzzles through accident analysis. Sometimes it is about thinking up better designs for equipment, workplaces, and systems. This blog is about good design and bad design, accident analysis and how it can be done better, and how we can make a better, safer world by design!
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