Discovering How Riding on the White Line is the Most Efficient Way to Bike.
Experiments, Notes, and Hacks of an Engineer Biking Across America
I had intentionally placed my speedometer on my top tube, off of my handlebars keep it out of sight, but after a few days on the bike, it’s hard not to be tempted to gaze down and continuously check your speed.
After the undulations of the Pennsylvania hills (AKA the Appalachians), I thought the relatively flat roads of Ohio and Indiana would be smooth sailing. My daily average speed would hover somewhere around 13–14 mph, but the variation was +/-5 mph at any given time. I had some pretty aggressive plans aiming to ride roughly 100–120 miles /day — but with fluctuations of 30%, it made predicting the day’s ride time wildly tricky.
I had been on some gravel trails, and the difference between the trail and road was night and day — every vibration and rattle signaling wasted energy. But on these flat roads, I couldn’t figure it out, until I rode along a long stretch of freshly-paved asphalt and was coasting — the difference was almost the same as the switch from gravel to a regular road!
As I rode, I tried to model what was happening and it brought me back to the good old Free Body Diagrams from Physics Class.
When you’re biking, most of your energy is going to combatting two opposing forces: rolling resistance and aerodynamic drag (more about that one later).
The force of Rolling Resistance = Normal Force (the weight of me and the bike and all my gear) * Coefficient of Rolling Friction.
If the weight stays constant, the and the road is flat then any deceleration is due to variations in that friction coefficient.
I was curious about this — how much the variations rolling resistance of the road would affect my speed, so I wanted to come up with a little experiment to rate the road conditions.
So here’s what I did:
- Found a flat, straight section of road
- Pedaled up to 20mph and tried to keep it constant for 10 seconds so that I knew I wasn’t accelerating
- I would stop pedaling and coast to see how far I could go before I got down to 10mph
Repeat three times to find the average. With this test, short coasting distances meant lots of resistance, while a long coasting distance implied a smooth surface.
These were the ratings:
- Small Aggregate Road: 0.17 Miles
- Large Aggregate County road: 0.12
- Oil Sprayed Gravel: 0.07 Miles
- Fresh Asphalt: 0.25
- Average Road: 0.15 Miles of coasting
It shocked me — that the road conditions were that different — and other than Wind Resistance, the main force fighting back on me was Rolling Resistance. A 40% difference was mind-boggling.
What could I do to reduce rolling resistance?
- Overinflate tires — increased pressure reduces the deformation of the tire, which is lost energy — but leads to a bumpier ride! I was already riding at ~120 PSI, which is close to the tube limit.
- Reduce Weight — Continue to pare down my gear, and strategically carry water
- Ride on a smooth road — but should I go out of the way to find fresh asphalt?
Often, the finer — but perhaps more expensive to maintain — asphalt was found in the cities, while the coarser aggregate was used for rural county roads. So the smoothness of road surfaces varied so much between US Routes, State Routes and even within Counties and across states — and there’s not much you can do to control it.
I found my self riding one day though riding on the white line when the shoulder was only about a foot — something I usually kept clear off in the busier roads of the East. But much to my amazement, it was like riding on rails!
The thick, reflective paint used was often raised about 1/4” off the road surface, and filled all the crevices between the stones leaving a smooth 4”-wide stripe that was nearly continuous.
The rating for the white line: 0.23 Miles — almost as good as a fresh road!
The white shoulder line provided respite from the vibrating roads and gave me just one more piece of control back. And so, I found myself riding roughly 700 miles out of 3358 on the white line, saving me hours of energy.
You can’t choose the conditions of the county roads, and you can’t change the conditions of our environment, but you can change how you approach them.
Riding the Line: In the summer of 2018, I spent five weeks riding my bike solo 3358 miles from Boston to San Francisco — fulfilling a boyhood dream, and raising funds for STEM Education programs at the Lemelson-MIT Program. As an engineer, with many hours to myself on the bike, while I had many cultural experiences across the country, I found my mind naturally wandering to trying to make sense of the physical world around me, and how to ride more efficiently.
