Sunday, 28 January 2018

Nonsense Travels At 25mph

Anything which challenges UK dogma on what or who highways are for is often met with derision and in our current post-fact thinking of the world, emotive nonsense travels far more quickly than rational facts or critical thinking.

This week, I came across a website which concentrates on plans in London to build a so-called cycle superhighway through Chiswick in West London with the rally cry "ditch it or switch it". The consultation for the scheme closed in October last year, but one of the boroughs involved, Hounslow, has said that decisions will be put off until the summer, partly because of the London elections in May and partly because of issues raised about the Chiswick High Road section.

Anyway, that will have to run its course and I want to respond to the comments made on the "ditch it or switch it" website, although in truth, you can copy and paste this kind of sentiment into any scheme where streets are being proposed for rebalancing. It doesn't matter if you are talking about a single zebra crossing which "takes away people's parking" or a transformative scheme such as CS9. The key claim which caught my attention was this;

"The way things are currently, CS9 will destroy Chiswick High Road. It will make it far less pleasant to shop. Buses will be delayed. Traffic will crawl along spewing fumes. We will lose trees and the tables and chairs outside cafes. Pedestrians won’t be able to cross the road very easily. Our local independent shops will lose business. Exactly who in Chiswick will benefit from cyclists whizzing past at 25mph."

How was this particular speed picked - was it from design guidance? In design terms, we will be talking about a "design speed" which then (through mathematics and physics) translates into things like stopping sight distances, the radii of curves and bends, traffic signal timings and so on. The design speed is not going to be the speed at which most people will be cycling. Perhaps we can look at it more like a "maximum safe speed", or a speed within which most people will be accommodated safely.

The Design Manual for Roads & Bridges in Interim Advice Note 195/16 suggests;

Well, 40kph is is 25mph, but a 3% gradient is 1 in 33 - for every 33 metres travelled, one drops 1 metre - that is a pretty steep hill. The other figures range between 12.5mph and 18.75mph. Remember, this is a design standard for trunk roads and motorways and therefore anything designed to this will probably be rural. 

These design speeds provide lots of margin for error and will rarely be applicable in an urban situation. Chickwick High Road does not have a gradient of 3%, it's not rural and so 25mph is never going to be a sensible or even an achieveable design speed. Of course, the carriageway of Chiswick High Road is 30mph, but driver speed never seems to feature in the concerns of those who are against providing cycle tracks.

In the creaky and out of date Local Transport Note 2/08, we are provided with some design speed advice;

So, the guidance talks about a design speed of 20mph with an average speed of 12mph. The point about momentum is an interesting one because with the "traditional" UK approach of bolting on cycling to walking space, we end up with side roads and obstructions impacting on the flow which one would otherwise cycle at. It also reinforces the margin of safety I mentioned about.

They look the part of "fast cyclists", but they are simply
not going to be able to maintain a Tour de France speed.
OK then, who exactly cycles at 25mph? In 2014, I completed the RideLondon London-Surrey sportive. It was the year which got cut back to 86 miles because of a storm. Including stops, my average speed for the 86 miles was 11.12 miles per hour. On the first 17 mile stage from Stratford through Central London, my average speed was 16.19mph. Anyone who has ridden this will be able to confirm that the first part is downhill and the rest is mainly flat, so a top speed isn't going to be getting over 20mph very often, unless one is riding a full-on racing bike and knows how to use it!

Racing bikes, training and closed roads are still not going
to be able to get most people cruising at 25mph.
RideLondon is on closed streets and even the most amateur fun rider (like I was) is going to have to have completed some training to be able to tackle it. There are going to be people out there who can top 25mph. People such as Chris Froome who averaged 25.47mph in the 2017 Tour de France. But hang on, we are talking about flat West London, not the hills and valleys of France. That's the thing about averages, though, they smooth the numbers out and so while our Chris might have been blasting down some hills, he would have been crawling up a few too.

25mph for people using cycling for every day transport is demonstrably nonsense. It doesn't happen and it is disingenuous to suggest otherwise, although it does rather suit a particular style of narrative. Personally, I cruise (average speed) at about 10mph on my commuter bike which is a big heavy, upright hybrid. If I am on my tricycle, my cruising speed is about 8mph. It is a long, long way from 25mph.

People feeling safe won't have to worry about keeping
up with drivers. They can relax and take it a little easier.
There may be fears about how cycling may change an area because of the way in which highway space needs to be rebalanced. If people stuck to that, then they would perhaps be a little bit more honest about their fears. Perhaps some people who don't cycle can only see the young white male cycling on their streets at the moment. This small group of people will be more likely to be moving towards the higher end of the design speed, but being on the carriageway, it's a defensive tactic. This is what you get if you design for cycling as a bolt-on to driver space.

A group of tourists on a safe cycle track. They are seeing
the sights, they're not a racing team.
As with designing streets for driving, we can influence the speed and behaviour of people cycling through design, especially where we need to give clear instructions on how people should deal with the interaction of others such as the approach to a bus stop. However, the key difference between cycling and driving is that the strength, power and endurance of people cycling varies hugely, whereas the motorised transport essentially levels these differences.

A sedate commute, enabled by the protection. This chap
might be your target customer on a rebalanced high street,
rather than the people driving through at 30mph.
What this leads to is where cycling infrastructure is well designed and attractive, then everyone can use it and above a minimum flow (which will depend on location), the "slower cyclists" will help influence the speed and behaviour of those who are more capable of nudging the higher end as they ride. In short, good infrastructure creates the conditions to enable a wide demographic to cycle and in turn speed and behaviour is moderated.


  1. When Ive done RideLondon, I've done the first 25 miles in an hour. This is very fast for me (my total times when it was 100 have all been over 5:30).

    Very rare I go that fast on even Sunday club rides- usually a cruising speed of 19-20mph with a target average of 17.

    25 average on early part of RideLondon has been down to riding in big groups that are able to fully unleash knowing that the only things on the road are other cyclists going in the same direction, with the whole width of the road available, traffic lights are to be ignored and there's no-one to give way to.

    day to day, 25mph is a speed only frequently achieved on the flat by racers, by time triallers etc. It's very, very quick.

    1. Indeed - every day transport cycling doesn't come close.

  2. You're right about cyclists' cruising speed; that's not the main issue. The key thing is priority, because stopping then reaccelerating to cruising speed wastes so much energy. The energy lost in decelerating from 15km/h to 0 km/h, then reaccelerating to 15km/h is equivalent to the amount of energy needed to travel 70 metres at a constant speed of 15km/h. This is huge.
    Unfortunately many separatist designs place the cyclist at the left of the carriageway, and give priority to all cross traffic at side roads, driveways etc.
    Say there are six such intersections in one kilometer of separatist cycle path: 420-meters worth of energy is potentially lost: a 40% increase in energy consumption comparing with continuing to ride with the priority traffic on the main carriageway.

    1. Having people cycling give way at every access and junction (with a protected layout) is essentially a waste of time and that is why continuity is so important.

  3. Regarding your last paragraph, as long as the cycle path is wide enough for faster cyclists to safely overtake then I have no problem. I'm a faster cyclist because it's the only practical way for my commute to work (I don't live within 2/3 miles of central London like so many utility cyclists) and I feel those of us who commute a greater distance should be catered for. Current cycle superhighways leave a lot to be desired unfortunately

    1. Some of the issue with the best CSHs (ie the core of CS3 and CS6) is (anecdotally) that they are popular to the point where people divert to use them and cycle slightly further because they are nicer. If there was truly a grid of similar quality, then the load would be spread.

  4. It's interesting that the 'margin of safety' to which you refer applies to cyclists, and not to pedestrians.

    The proposed CS9 design incorporates a number of "crossing points" for pedestrians. These are unregulated; there are no traffic lighnts, there are no zebra markings. Yet according to TfL at a public meeting, pedestrians have the right of way if crossing the cycle track at one of these points.

    Perhaps this is in an effort to maintain the "momentum" to which you refer. But many pedestrians are already wary of crossing marked zebra crossings when a cyclist is approaching, because many cyclists (presumably to maintain that 'momentum') will weave around a crossing pedestrian rather than stop.

    To a pedestrian, a cyclist approaching at even 10mph is a hazard because, as Mr Carnall suggests above, cyclists don't like stopping and starting.

    We are talking, in the case of Chiswick High Road, of a shopping and residential street, not an arterial road (where momentum can be maintained). Pedestrian need to cross to get to the shops, to get to bus stops, to access the cafes, homes, churches and businesses on either side of the road.

    Therefore on both sides it is not sensible to put this design of segregated two-way cycle track on a High Street. Cyclists do not want to stop ('lose momentum') to allow pedestrians to cross, and the priority on unmarked crossings is impossible to police.

    To maintain momentum, to protect pedestrians, and to provide access to shops and other premises, this design of cycle track should be located on an arterial road - and not on a busy local High Street.

    1. "To a pedestrian, a cyclist approaching at even 10mph is a hazard because, as Mr Carnall suggests above, cyclists don't like stopping and starting."
      You know what cyclists like even less? Hitting a pedestrian.
      10mph is a very normal speed for Dutch cyclists, who don't like to stop either, but, you know, you make eye contact and work it out.
      Give it some time. You all just need to get used to this new infrastructure and the new users on it.

  5. I do agree that separatist cycle infrastructure can cause problems for pedestrians, who should always have priority on city streets. If pedestrians and cyclists are having a hard time, it's a sign that the motor traffic should basically be excluded altogether.

  6. Other places that have started with the attitude that providing cycle facilities will be the end of the world, have found that custom in shops increases and a better environment results. One business owner (can't remember where) was strongly against a cycle route, after implementation he was happy with the increased custom.

  7. They always seem to come up with such spurious arguments.

    Buses will be delayed.
    Are they dropping a buslane for cs9? If not then cars are likely the current impediment to buses, cs9 should remove some cars.

    Traffic will crawl along spewing fumes
    Same as ever then, induced demand, more bikes = less pollution spewing vehicles

    We will lose trees and the tables and chairs outside cafes.

    Pedestrians won’t be able to cross the road very easily.
    Bikes move slower than cars, suggesting bike lanes are harder to cross than "car" lanes us utter rubbish. I see some concerns over pedestrians crossing bike lanes which in isolation may be valid, but they seem to ignore the fact that people already have to cross a busy road.

    Our local independent shops will lose business.
    Citation needed! Cars driving straight past add little business, cycling is thirsty work, cafe stops are an integral part of cycling to many. Other schemes have shown increased business.

    You've already covered the 25mph nonsense. I'm quite fit & ride light bikes but my cruising speed is only about 17 on the flat between junctions, my average is usually ~12 in urban areas.

    1. Can I just address your comment that "suggesting bike lanes are harder to cross than "car" lanes us utter rubbish"?

      Cars are halted by controlled crossings, while pedestrians have priority on zebra crossings. These do not apply on the proposed cycle lanes, which have "unregulated" crossing points.

      Pedestrians are frightened of crossing these cycle lanes because cyclists tend not to stop for them. Cyclists do not want to break the "momentum" referred to above; they already weave around pedestrians on road crossings, and so pedestrians, particularly the elderly, are frightened of attempting to cross in front of cycles.

      In addition, there is no midpoint at which to pause crossing a two-way cycle lane. A pedestrian crossing a "car lane", as you put it, can often look in one direction and cross to the middle, then look in the other before completing the crossing. To cross a two-way cycle lane, one must be clear in both directions at once.

      For all of these reasons, it is indeed harder for a pedestrian to cross a two-way cycle lane than to cross a road.