Читать книгу Proficient Motorcycling - David L. Hough - Страница 27

I often use the phrase “adjust your speed to sight distance.” Let’s be specific about what that means. At a given speed, it takes a certain minimum distance to stop a specific motorcycle. If you expect to avoid that porcupine or those motorcycles splattered on the pavement just around that next blind turn, your speed must be limited to your stopping distance. For example, let’s say your machine is capable of coming to a stop from 60 mph in 190 feet. If you can’t see any farther ahead than 190 feet, your speed shouldn’t be any faster than 60 mph. If your sight distance is limited to 150 feet, you shouldn’t be riding any faster than say, 50 mph.

Of course, trying to judge distance in feet or car lengths is unreliable. The pavement goes by in a blur, too quickly to make easy mental measurements of distance. The trick is to make time measurements. While you’re riding along, pick out some fixed object ahead such as a signpost, and count the seconds it takes you to get there. Count out loud, “one thousand and one, one thousand and two,” and so on. By taking a time measurement of your sight distance and comparing it with your speed, you can make more intelligent decisions about how far you are hanging it out.

I’ll offer some guidelines:

Speed	Minimum Sight Distance
30 to 50 mph	4 sec
50 to 60 mph	5 sec
60 to 70 mph	6 sec
70 to 80 mph	7 sec

Give these numbers a try, and see if you agree with my suggested minimums. If your reflexes are really quick and you can make consistent hard stops without dropping the bike or highsiding, shave off a second. If these minimums make you a little nervous, add a second. The point is to have a method of gauging honestly how your speed stacks up to your and your bike’s stopping performance. If you find that you are consistently entering blind situations at speeds too fast to stop within your minimum sight distances, the message should be obvious: get on the binders and slow down quickly whenever sight distance closes up.

When you are approaching a blind situation such as the crest of a steep hill, is it reasonable to assume that there isn’t a problem ahead, even though you can’t see the road ahead? For instance, let’s say there is a driver on the other side of the hill backing up to make a turn into a driveway. Should you brake just because your sight distance is temporarily limited? Personally, I have seen enough hazards just over a hill or around a corner to be very suspicious. I don’t think it is reasonable to assume the road is clear when you can’t see the road ahead within your stopping distance.