The [part of the] road less travelled: car economy gains by ridge-riding in the dry?
 

As the title implies, is there anyone who has noticed a non-negligible improvement in fuel economy by driving on the unused portion of lane tarmac (typically on the inside half of the lane) when operating a car in dry conditions?

On one hand, logic may dictate that the used portion of a road lane (typically the centre of the lane) would be rendered smoother by the constant traffic which uses it. It is easily noticeable by often being darker and slightly lower than the unused portion on the inside which appears more glossy and new. On the other hand, I have noticed that the unused portion actually feels smoother, and is less prone to potholes.

I am not sure if this different experience is simply due to wishful-thinking induced by driving on fresher-appearing tarmac, however.

Summary version: I've only heard of ridge-riding really working when water forms in ridges of roads in poor condition. Does ridge-riding really work in the dry?

The ridge is good for avoiding potholes. It would be nice to not trash the tires and shocks.

regards
mech

I crowd centerline on roads with deep truck trenches because it's much smoother out of the trench.

:D Yes! wishful thinking and/or pothole avoidance!

According to Cummins, the difference in CRR between smooth polished concrete and chip and seal blacktop is 45%. As a rule of thumb if you can hear your tyres roaring against the road surface, your MPG is suffering.

Stick to where it's polished smooth :thumbup:

On the chip seal we have so much of here, the ridge is the worst. In the grooves, a lot of the pebbles are mostly cleared and I tend to do better.

Especially in areas where they allow studded tires, there is much less road noise (and I believe better FE) by driving out of the "normal" position in the lane. For me in OR, that meant two wheels on or around the edge stripe of the road, and two near the center of the lane. Studs seem to chew up concrete or asphalt really badly...

I've noticed similar phenomena on a few roads here in the SF Bay Area of CA, where studded tires are not used. But it's much less common--and the edge of the road often has other debris on it (even just gravel) that can lead to extra noise and extra resistance.

-soD

Studs illegal in Va, COME SLIDE WITH US LOL. It does help the roads but the asphalt parts are really trashed.

regards
mech

Except that traffic generally does not polish the surface, but roughens it. Especially with concrete, as the cement is worn away, exposing the rougher aggregate.

With the Insight's instant mpg gauge, I can definitely see a difference between the ridges & ruts, and between different road surfaces.

I don't know about 'generally', but fresh concrete will be polished smooth until the aggregate starts to break through. We don't have any concrete roads so I don't know how long that takes.

For asphalt, that tends to melt/ soften in the summer sun, the grooves take on a distinctive shiny/ polished look, they're definitely smoother, but there comes a point where they start to 'buckle', pot holes appear and are filled in etc. If you're suspension has to do more work, that's lost energy too.

A lot of it will come down to the age and maintenance of the road in question.