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When entering traffic from an on-ramp, how many times should you turn your head and check traffic?

If you say “zero” or just use your mirrors, you’re a moron and will become a hood ornament soon enough.

Lately, I’ve been reading a book by Larry Grodsky called “Stayin’ Safe”. This book is a compilation of a bunch of the safety columns he wrote for Rider magazine. While Larry’s observations have been interesting and enlightening, I’m not a big fan of his writing style. But he does encourage you to ask questions instead of just accepting the current status quo of what the “safety experts” preach. How many fingers should you use on the front brake? Is there really a one-size-fits-all answer?

One of Larry’s recommendations, related to headchecks, is that while they are necessary and prudent for all riders, that taking your eyes off the road ahead is dangerous. And that the only way to minimize this risk is to check just once, and as quickly as you can.

I completely disagree!

I say three times, and here’s my reasoning (Warning: I’m about to use science and calculus. Geez, I never thought I’d use that form of mathematics for something like this).

First, remember as Larry suggests, your looks should be very brief, almost like snapshots.

The first time you look, your brain gathers information about your relative position only. You see where you are in reference to all the other road users. In math, you can give this snapshot a value of “x”. If you stop looking at this point, you have no way to tell anything except where everyone else is, but nothing about how things may change in the coming moments.

The second time you look, your brain is able to process velocity information. This is because you are gathering new positional information with the added component of a change in time. In calculus, a change in position, delta x (dx), divided by a change in time, delta t (dt), yeilds velocity (v = dx/dt). That’s why we express velocity in unit like miles PER hour. This second look tells you how fast everyone else is moving. While most folks would be content to stop here (and you might be justified 95% of the time), without knowing whether someone is speeding up or slowing down (acceleration/deceleration), you can’t make the best decision about you immediate future. Like when that person coming up from behind decides maybe they can beat you to that gap if they “put the hammer down”.

The third time you look, your brain can gather this acceleration information. Again using calculus, a change in velocity, delta v (dv), divided by a change in time, delta t (dt), yeilds acceleration (a = dv/dt). This information tells you brain not just how fast someone may be approaching you, but also whether they are changing their rate. This can be of particular importance because many other drivers will change their speed based on your position in order to let you in or race you to the gap.

Of course timing your headchecks far enough apart to gather the most information and planing the last one to correspond to a couple seconds before you’ll have to make your move is also highly recommended.

If no one’s around, then 1 headcheck is probably enough to give you the information you need. If there are other vehicles around, but they aren’t real close, you can get away with 2 headchecks which will tell you if anyone is coming with a head of steam. But if there’s some serious traffic going on, with 3 headchecks, you can get all the details you need to make the best decision about how to blend into the traffic stream. Just don’t spend too long with your eyes diverted from the most accident prone area between 10 and 2.

Rhino