Why is cycling on a road so much faster than cycling on a cycle path?

Question

I normally cycle on a cycle path and I struggle to go over 10Mph on my bike for any distance. My Daily commute took me 58 to 42 minutes depending on how much I push myself.

This morning and yesterday evening I decided I'd try to cycle on the road rather than the path. The distance is only 0.2 miles shorter by road but it only took me 34 minutes because I was travelling at 10 to 14 Mph most of the time sometimes faster on hills. I had to stop at more traffic lights but it still took a heck of a lot less time.

Any idea why this happens?

I ride a mountain bike with Semi slick tyres if that makes any difference.

Answer 1

Given the same day and the same rider and otherwise equal conditions, riding on a tarmac road vs riding on a gravel cycle path, the road will be faster.

Why?

It's about the rolling resistance of the surface.

This page gives a good breakdown of the physics involved in working out how much power you need based on various inputs.

But basically, a rougher surface offers more rolling resistance to your bike tyres, so you need to put more power in to sustain the same speed. Given you're likely to put out a constant power (since we're assuming identical rider and conditions) on both track and road, since there is less resistance, you'll go faster on the road, the 'spare' power will come out as speed.

Given identical surface, then you have to look at what else is different in the route. There's a 0.2 mile difference in distance, but, what's the ascent and average gradient of both routes? Plot them on bikehike.co.uk (or the mapping tool of your choice) and see what the difference is.

A local route to me on the Trans-Penine Trail turns out to be a 2% gradient, though it looks flat, on gravel. The road route near by has some sharp hills, but has downhill segments and a much smoother surface, so is faster on my MTB and far faster on my road bike.

Also, on the road are could be benefiting from the drafting effect of cars possibly, whereas on the cycle trail you might be cutting the air yourself, that can account for a 20% energy saving.

And finally, for now, there's always the right of way, if you're having to slow on the cycle trail to negotiate slower cyclists or other route users, whereas on the road you're the slow thing people are moving round.

Answer 2

In the UK, cycle paths aren't really set up for cyclists! They seem to be arranged by planners more interested in meeting targets for miles of cycleway. They are also aimed more at leisure cycling than for people who want to use their bike to go places.

One of the problems that I find in the South East of England is that the cycle paths often take away the normal rights of way that apply to road users. In particular they share pavements so pedestrians are getting in the way and you have to give way when you cross side roads (as opposed to having right of way as a road user).

Answer 3

Assuming you know your own body, the route and the climatic conditions very well we can try and rule out variations in these - however I would suggest that this sort of variation can be very dependent on conditions. Think we have a few questions on this, even including air temperature and pressure effects.

If we do rule them out, a contributing factor can be the surface - cycle paths are often a different, rougher, surface than roads, and this can increase your rolling resistance considerably.

Also, how close to the road route does the path follow? This could cause a difference, depending on your optimum power output and the gradients of the road and path.

Answer 4

Traffic on the road gives you a pseudo-tail wind.

I have a road in my commute that has an on-road unprotected cycle lane of about 120 cm wide. Its far too small for a car to park in, and difficult to pass another cyclist. The lane is about as small as it can be and remain legal. Its a 60 km/h speed limit though with traffic it rarely gets that fast in my commute window.

There's an exceptional draughting / drafting effect from passing vehicles - even though you're not behind them, they generate a definite stream of air in the direction of travel. I've done sustained efforts of 40 km/h on this road when other parts of my commute drop to 32-35 km/h

You'll feel it more if a non-aero shape like a truck or bus passes; its like a gentle tailwind for a few seconds.

You can also visually see this effect on a still foggy day near a main road. The fog can hang over surrounding areas but there's a "tunnel" of clarity in the fog that tracks the roadway. That is cleared by the wind effect of passing vehicles, showing where the air is moving.

Downside - an unprotected cycle lane is 100% useless at protecting you from badness. Being so close to moving traffic is reducing your overall safety.