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