I hope to get some resources to continue the microsimulation work on buses and bikes and will update this blog when I’m able to take the work forward. In the meantime, I was planning something on the new Superhighways consultations (due Wednesday: keep your eye on the Consultation Hub), when I found something quite interesting related to bus-bike modelling in the TfL Board Papers from February. (Londoners really do need a couple of cycling reps sat on the TfL Board).
TfL hasn’t modelled detailed interactions between buses and bikes, as per my plans. However, what it has done is looked at an aggregate level on how changing cycle flows are affecting the network. For most contexts, this high-level view wouldn’t be that helpful, as I explained in my earlier post (cycles tend to disappear in the mix, as their numbers are low and their average speeds the same as buses). However in Central London, because of its special characteristics, even the blunt instrument of aggregate modelling is now flagging up some of the impacts I expect microsimulation to bring out in more detail and in other areas.
The key point I take from the paper is that discussing ‘will new cycle provision delay buses?’ is kind of beside the point. TfL’s modelling finds that existing cycle provision in the form of shared bus lanes will delay buses as cycle flows grow. Much of the increase in cycle trips is happening along major roads, often in bus lanes, at peak times in Central areas – exactly where, and when, the network is already heavily congested. So even without modelling interactions between buses and bikes on the network, just adding up the numbers shows the increase in cycling is pushing bus lanes over capacity, and this impact will increase. So we need cycle – and bus – planning and infrastructure that mitigates the delays due under Business as Usual.
Quoting from the Board paper itself (page 19):
‘with or without the Cycle Vision investment – population growth, increased cycling levels and increased traffic flows are likely to result in delays occurring for general traffic and buses in central London (if not mitigated). The modelling therefore provides an articulation of how change on the network may be experienced, and the impact of delays to traffic can be quantified in monetary terms to enable the scale of impact to be determined. For example, these are estimated to total around £10m per annum (undiscounted rate) for general traffic and around £9m per annum (undiscounted rate) for buses in central London – if no mitigation was put in place.’
In other words, the increase in cycling we’re seeing is going to result in some substantial delays to buses, as well as other motor traffic, on the network as it stands (with heavy reliance on cyclists using bus lanes, which are not ideal for cycling but often better than alternatives).
The paper continues:
‘This, of course, is not going to be the case in practice, as a substantial programme of improved network management and mitigation is planned, and elements of this already underway. Hence, these figures should only be viewed as illustrative. In addition, the Cycling Vision infrastructure schemes (the Central London Grid, Quietways and Cycle Superhighways) are shown by the modelling to mitigate some of these delays, by drawing cyclists onto quieter roads and through the provision of segregated facilities in some locations. In addition modal shift from car and other motorised vehicles to bicycles, while not able to be captured by the CLoHAM model used, in practice is likely to further mitigate these impacts.’
In other words, separating cycles from buses at street and route network level will help reduce bus delays that will otherwise take place as cycling increases. (And probably vice versa, although the concern here’s for public and private motorised journey times). The modelling still doesn’t include mode shift to cycling, which will in practice further improve matters (particularly, I’d argue, if we put in really good infrastructure to attract new users).
And on page 23:
‘The modelling does show that the cycling infrastructure interventions will help mitigate the impact [on buses] of additional cyclists on the network.’
We still need the microsimulation to more fully understand these impacts, especially outside Central London, and better mitigate them at route and street level. However, what’s really interesting about this paper is that the aggregate modelling indicates separating bikes and buses is a form of mitigating bus delays that are otherwise inevitable. So it may not be so much a question of ‘if we put in this cycle track, buses will be delayed by 30 seconds at peak‘ as ‘if we don’t put in this cycle track, bus lanes are going to start grinding to a halt five years hence’. Which will be unpleasant and frustrating for bus passengers and cyclists alike.
Hopefully, this is leading to a more strategic re-thinking of where we should put the bus and cycle priority routes, which will need to be allied to an in-depth understanding of current and potential cyclist behaviour. (In other words, no, you can’t just direct cyclists onto a confusing detour on a ‘Quietway’ that’s really a rat run. They’ll still be in your bus lane).
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