Cobham Bridge – Wider paths

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Adding foot path width to a steel bridge looks easy, below is an example from New York.

First a bit about safety – Every second month a driver of a motor vehicle makes a mistake at the 35 km/h corner on the western end of the bridge.

Clearly the speed difference between the present 80 km/h legal speed limit and the design speed are too far apart, NZTA knows safer speeds improve safety and in the future the legal speed limit along Cobham Drive will be 60 km/h.

Transport Modelling Report – Southern Links 22/11/2013  AECOM Job No.: 60164546 / 3.6.3 – page 41.

For now Cobham Bridge is one of the heaviest trafficked 2 lane section of road in Hamilton, its 2017 traffic count of 31,100 vpd was up from 30,700 vpd in 2016. Fairfield Bridge show there is a maximum capacity a road can carry. Cobham Bridge has not yet reached its growth limit. Let’s say the ‘ideal’ vehicle lane width is 3.5m with 1.8m clearance, with a theoretical capacity of 34,000 vpd. If the volume capacity was reduced by 70% of the ‘ideal’ by changing the lanes widths to 2.8m for motor vehicles and 1.8m for cycle lanes, the maximum vehicle capacity could be about 23,000 vpd which is roughly a third less than the 2017 count of 31,100 vpd. Is it possible in 2021 when the Hamilton bypass is open and traffic volumes drop, to change the lane widths to suit 33% less motor vehicle traffic?

Going back to the start of this post, on-road bike lanes are okay for fast and confident cyclists or E-bike riders, but for the 8- or 80-year old cyclist they are unlikely to feel safe. Adding width to the existing paths looks like a sensible thing to do.

Category: News

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