A few weeks ago I was on a ride that took us that part of Province Line Road that's closed to vehicular traffic (bicycles aren't vehicles in NJ, go look it up). Someone asked how steep the climb on the south side of the bridge over Stony Brook was. I said it had to be less than 26%, because I know by experiment that I can't keep the front wheel down at that grade (I never stand on the pedals, as many cyclists do when climbing a steep grade; I'll get off and walk if the grade is too steep to pedal).
Another cyclist (with more experience than I have) said that the grade at that point was about 8% or 9%... but after having just ridden it, I knew it had to be steeper than that; I was working far too hard at one point for that to have been the grade. So I resolved to go out and measure.
Now, according to the US Geological Survey,
Percent of slope is determined by dividing the amount of elevation change by the amount of horizontal distance covered (sometimes referred to as "the rise divided by the run"), and then multiplying the result by 100.
So I decided to take my four-foot level and a metal tape measure, and go find out the numbers.
Why a four-foot level? Well, I know from measuring the distance between the hubs that the wheelbase of the Yellow Maserati*, my titanium bike, is just under 39". So a four-foot level is about the length of the bike. I figured I could rest the uphill corner of the level on the road, hold it so that the bubble showed level, and drop the ruler from the other end to the road surface to get the difference in rise. And four feet would be big enough that I could measure to the nearest quarter-inch, and still have useful accuracy. I'd be creating a right triangle, with one of the non-hypotenuse sides of four feet, and Pythagoras implies that the hypotenuse (in this case, the road surface) has to be longer than either of the other sides.
So on a morning that didn't get above freezing, the determined detective might have found me sitting on the cold pavement above the bridge over Stony Brook on Province Line Road, taking measurements.
I first took the measurement just at the point the road begins to climb on the south side of the bridge. with one end of the level on the road surface, the rise at the other end was 4 ¼" - just about 9%.
It still didn't feel right. I noticed a steeper spot further up the hill. I took two measurement there; one was 6 ¾", and the other was a shade over 7". Aha! Just about 15%. Nowhere close to the 26% I'd thought, but much more than the 8-9% reported by the fellow cyclist.
I suspect this is a "measuring the coastline" problem. Mapmakers (aren't you glad I didn't say "cartographers"?), geographers, those who study fractals... all point out that the measurement of a coastline depends on the unit of measure you choose, and the smaller the unit, the longer the coastline becomes (even though the area of the land it encloses is unchanged). If your unit of measure is a mile, you'll get a certain distance, but you'll miss much of the detail of the coastline. If your unit of measure is as small as a grin of sand, you'll get much more detail (and a much longer coastline!).
In the case of Province Line Road, I suspect the grade out of the bridge is 9%, at some longer unit of measure than I used. But when you're pedaling a bicycle out of there, a unit of measure about as long as the bike is probably more useful.
In other news, I've just confirmed the fact that I'm the kind of old geezer who will ruminate for weeks on a useless problem, and then go out on a frigid day with tools in hand to go solve it. And will then write a needlessly-detailed blog post about it, with references. That's got a certain "Get off my lawn!" energy to it, doesn't it?
*It's the Yellow Maserati because it was one in a series of midlife crisis purchases (as a yellow Maserati might be), and because it is, in actuality, neither yellow nor a Maserati. I was going through a "meta" stage when I was naming it. (I think I'm still going through that "meta" stage.)
I usually ride that south to north, but recently rode it heading south. I use a Hammerhead Karoo II which displays grade. At the start of each climb, a graphical representation of the entire climb, and grade by section overlays the map. Another screen shows current grade, although it is hard to watch when climbing out of the saddle. I looked at my Strava and it shows a maximum grade of 14.8%
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