It’s the Christmas silly season and newspapers are again rounding on cyclists (aka ‘lycra louts’) for running red lights and putting other road users at risk. Never mind the lack of any hard evidence of injuries or deaths caused by cyclists running red lights, it’s a story that appears to please news and online editors, such as at the Sunday Times yesterday and The Times today.

To borrow a memorable phrase from Peter Mandelson, I am intensely relaxed about cyclists running red lights, where it is safe to do so, i.e. when there is no obstruction caused to anyone using the junction who has priority at the time. Josh Hart has a great blog post on the subject.

Josh says it’s important not to confuse safe behaviour with law-abiding behaviour. “You can follow every law and still put yourself in a terribly dangerous position (i.e. in the door zone). By the same token, you can slow and look around carefully at red lights and stop signs and proceed when no one is coming and you’ll likely never get into trouble. Blindly following the law is a recipe for getting hurt on your bike. Better to trust your own hearing, sight, and instincts than the government’s rigid idea of ‘health and safety’.”

There’s some evidence to suggest that cyclists stopping at traffic lights on the left hand side make themselves more vulnerable to getting squashed by lorries and HGVs/LGVs that find it hard to see a cyclists in that position. This may explain why London Mayor Boris Johnson is considering allowing cyclists to turn left on red as well as riding the ‘wrong’ way down one-way streets as is already the practice in Brussels, among many other cities.

This would go some way towards addressing the second plank of Josh’s argument, that the Highway Code is inappropriate for cyclists. He say’s “unfortunately we live in a society where the needs of one class of road user are prioritised at the expense of more vulnerable road users.”

Buffalo Bill made the same point long ago on The Bike Show when he said that traffic rules were only needed to address the problem of automobiles on the roads, not cyclists, and therefore the rules should not apply to cyclists in the same way. As Josh argues, “The bicycle is a kind of a hybrid animal– somewhere between a pedestrian and a vehicle, and we need to treat it as such… Let’s stop trying to fit the round peg of cycling into the square hole of overly regimented traffic regulations.” Amen to that.

But before anyone accuses me of encouraging a free-for-all at red lights I strongly believe that to run a red light safely you need to have all your senses about you. You need to be looking hard enough to see that there’s no danger. You need to give way to pedestrians who have priority and anticipate those that have not yet stepped off the pavement. Setting traps to catch cyclists running red lights is so obviously an instance of wasting police time, though there is one small respect in which I do approve of Fixed Penalty Notices for red light jumping: If you don’t see the rozzer who nicks you, you weren’t looking hard enough to be safe running the red light, were you? So pay up and consider it a £30 lesson in cycle training. Sometimes when I’m cycling I can’t really be bothered with the effort involved in running red lights so I am quite happy to stop and wait, assuming there’s no potentially left-turning lorry looming over me.

What never seems to be discussed in the whole debate on red lights is why cyclists feel such a strong urge to run red lights, why it makes so much sense for us to do it. Those who write about it invariably ascribe it to the perceived arrogance and smugness of the cyclist, an expression of their innate sentiments of self-satisfaction and superiority. I feel a lot of things when riding the streets of London but superiority is rarely one of them. Certainly not when it’s pouring with rain and another bus has whistled past within a few inches of me, accompanied by a billowing cloud of filth and spray.

Cyclists run red lights not because we consider ourselves to be supreme beings but because of the forces of physics. The nature of the bicycle is that we have to use our own energy to move. Getting going is not simply a matter of disengaging the clutch with the left foot and easing the right foot onto the accelerator. When cyclists stop we have to give up all the kinetic energy we’ve built up and when we start again we have to overcome the inertia of our own body masss and that of the bicycle, the road resistance, wind, and so on. Cyclists running red lights are like people walking in a park who walk in the direction of where they want to go rather than following the paved paths. If enough of them are doing it, the result is a muddy rut in the grass. We don’t blame the walkers, we blame the planner who didn’t think about desire lines when making the paved paths.

It’s my sense that running red lights is much less about saving time than saving energy. A cyclist who runs red lights generally doesn’t save much time because she’ll usually end up stopping at a major junction at which point a law-abiding cyclist will have caught up, or nearly caught up. The vital point is that the red light running cyclist will have expended much less energy. And this is important. Cycling can be hard work, and the perception of effort puts a lot of people off riding bikes. The easier it is, the more people are likely to take it up. (By the same token, all those roadies who use their daily commutes to work out as a form of training, should perhaps reconsider their red light running, since stopping means they use more energy and therefore get a better workout. The expenditure of energy to get up to cruising speed might be considered as a form of interval training.)

All this is just my intuition based on my own experiences of cycling. I’d really like to find a physicist or an engineer who would be able to properly quantify the time loss and the energy loss involved in stopping at red lights. I think the results would be interesting and would help illiuminate the debate. The implications might go beyond the debate on red light running and could be useful for transport planners who, if you ask me, should be working hard to design routes for cyclists that minimise the amount of stopping that’s required. If you’re a physicist or an engineer who could apply your knowledge to these questions, please get in touch.