DataDan
Mama says he's bona fide
A few simple adjustments when approaching an intersection can put you beyond the reach of a vehicle threatening to cross your path.
In another thread recently, there was a discussion of whether a rider can prevent the dreaded but common crash with an oncoming vehicle turning left across his path. IMHO, he usually can, and I thought the topic deserved its own thread here in Training.
Though the immediate cause of an intersection crash--either with an oncoming left-turner or a vehicle crossing from a side street--is usually failure by the driver either to see the motorcycle or to perceive it as a threat, other factors can contribute to the error. Intervening vehicles or terrain may block the sightline between the motorcyclist and the driver, or excessive speed may be misjudged by the driver. But even when taking the recommended precautions--high-viz clothing, clear sightlines, reasonable speed--a driver might fail to see you. You would think, having exhausted your repertoire of good practice at that point, that your only hope for survival is a lucky impact and quality safety gear. Not to disparage the value of luck and gear, but you may still be able to avoid a crash by putting yourself out of reach.
The Theory
The tactics of this technique are easy enough to execute, but let's first look at the reasoning behind them, because a good understanding will help persuade you of their value. Approaching an intersection where a vehicle waits to cross your path, but still some distance away, you are in a safe zone. If the car begins to turn, you can avoid a crash by applying brakes or just rolling off the throttle. Much closer to the intersection you enter another safe zone. Here a collision is impossible because your speed will carry you through before impact, since the car must travel some distance to reach you. But between those two safe zones, you could be in trouble. If the car begins to move while you are in the middle zone, you can't stop before reaching the collision point and you can't clear the intersection ahead of the car.
Thus the strategy behind this technique is to reduce or eliminate that vulnerable zone. By adjusting your approach you can shorten that zone, often to nearly nothing. And under the best conditions you can replace it with a zone in which you can either brake to a stop or pass ahead of the car. Your approach then becomes crashproof: no matter when the other vehicle begins to move, you can avoid a collision. Of course, you're not literally crashproof. You could still make the wrong decision or lock the brakes, but at no point is a collision inevitable.
The time you spend in the vulnerable zone depends on your speed, your braking ability, and the time it takes the other vehicle to reach the collision point. At lower speed, with better braking reaction and application, and with greater distance between you and the other vehicle, the zone shrinks and may even disappear. Those are the adjustments this technique recommends.
The Rules
The advantage to this approach isn't just theoretical. It's possible in real-world situations to put yourself literally beyond the reach of a vehicle threatening you. Suppose you're going 40 mph, not covering brake, and approaching an intersection where an oncoming car waits to turn left 10 feet away from your path. You are exposed to an unavoidable crash for more than one second. If the car begins to turn during that interval, you will crash. But if you cover the brake, move one lane to the right, and slow to 30 mph, your exposure goes to zero. The car cannot touch you as long as you make the right decision and can brake effectively.
However, I must emphasize that other techniques for avoiding intersection crashes are usually more effective. It's much better to be seen and recognized so the oncoming driver doesn't move into your path in the first place. You avoid the split-second decision and the possibility of a crash under braking on a bad surface. So the measures described here should be incorporated into a larger strategy.
Also, it's important to understand that an intersection approach can't always be made crashproof. When speeds are high and the roadway is narrow, exposure cannot be substantially reduced. Improving your visibility to other motorists by maintaining clear sightlines and predictable speed is more effective because if they see you and yield right-of-way, they never become a threat.
But your primary strategy can fail if you encounter the truly clueless. When one of them happens along--and it's not so rare--the additional precaution of an intersection approach that reduces exposure could be a lifesaver.
My conclusions are based in part on a mathematical model described here: Intersection Kinematics (100K PDF).
In another thread recently, there was a discussion of whether a rider can prevent the dreaded but common crash with an oncoming vehicle turning left across his path. IMHO, he usually can, and I thought the topic deserved its own thread here in Training.
Though the immediate cause of an intersection crash--either with an oncoming left-turner or a vehicle crossing from a side street--is usually failure by the driver either to see the motorcycle or to perceive it as a threat, other factors can contribute to the error. Intervening vehicles or terrain may block the sightline between the motorcyclist and the driver, or excessive speed may be misjudged by the driver. But even when taking the recommended precautions--high-viz clothing, clear sightlines, reasonable speed--a driver might fail to see you. You would think, having exhausted your repertoire of good practice at that point, that your only hope for survival is a lucky impact and quality safety gear. Not to disparage the value of luck and gear, but you may still be able to avoid a crash by putting yourself out of reach.
The Theory
The tactics of this technique are easy enough to execute, but let's first look at the reasoning behind them, because a good understanding will help persuade you of their value. Approaching an intersection where a vehicle waits to cross your path, but still some distance away, you are in a safe zone. If the car begins to turn, you can avoid a crash by applying brakes or just rolling off the throttle. Much closer to the intersection you enter another safe zone. Here a collision is impossible because your speed will carry you through before impact, since the car must travel some distance to reach you. But between those two safe zones, you could be in trouble. If the car begins to move while you are in the middle zone, you can't stop before reaching the collision point and you can't clear the intersection ahead of the car.
Thus the strategy behind this technique is to reduce or eliminate that vulnerable zone. By adjusting your approach you can shorten that zone, often to nearly nothing. And under the best conditions you can replace it with a zone in which you can either brake to a stop or pass ahead of the car. Your approach then becomes crashproof: no matter when the other vehicle begins to move, you can avoid a collision. Of course, you're not literally crashproof. You could still make the wrong decision or lock the brakes, but at no point is a collision inevitable.
The time you spend in the vulnerable zone depends on your speed, your braking ability, and the time it takes the other vehicle to reach the collision point. At lower speed, with better braking reaction and application, and with greater distance between you and the other vehicle, the zone shrinks and may even disappear. Those are the adjustments this technique recommends.
The Rules
- An improvement you can make long before the situation even arises is to practice braking. You don't need MotoGP skill to ride safely on the street, but you do need to be able to apply the brakes quickly, smoothly, and confidently in an emergency without locking them up. Less braking distance results in less exposure. In addition, many non-crashes turn into crashes simply because an unpracticed rider panics and locks the brakes. See David Hough's book Proficient Motorcycling for tips on better braking.
- The easiest adjustment you can make to reduce vulnerability when another vehicle threatens to cross your path is to cover the brake lever. You decrease reaction time by a half-second or so because you don't have to move your fingers from the throttle to the brake, and that's a half-second less exposure.
- You can also reduce exposure by increasing the distance the other vehicle must travel to reach the collision point. The greater the distance, the more time it will take to reach you, and the longer you have to react. If it is an oncoming vehicle turning left or one crossing the intersection from the left, increase your space cushion on the left by moving right. Shift from the left side of your lane to the right or, better yet, move a full lane to the right. For a vehicle on the right, move left.
- Finally, slow down. Because stopping distance decreases a lot with a small drop in speed, you reduce your exposure with even modest deceleration. David Hough's recommendation to "slow down by 10" as you approach a potential hazard is a good rule of thumb.
Sometimes it's necessary to slow way down. If a driver is creeping into the intersection, he is increasing your risk by stealing your space cushion. One tactic is to veer toward him to freeze his motion then swerve away to reclaim your cushion. Or you can counteract the loss of space cushion by continuing to slow. At the extreme, keep slowing down as long as he creeps to make sure you can stop before reaching the collision point.
The advantage to this approach isn't just theoretical. It's possible in real-world situations to put yourself literally beyond the reach of a vehicle threatening you. Suppose you're going 40 mph, not covering brake, and approaching an intersection where an oncoming car waits to turn left 10 feet away from your path. You are exposed to an unavoidable crash for more than one second. If the car begins to turn during that interval, you will crash. But if you cover the brake, move one lane to the right, and slow to 30 mph, your exposure goes to zero. The car cannot touch you as long as you make the right decision and can brake effectively.
However, I must emphasize that other techniques for avoiding intersection crashes are usually more effective. It's much better to be seen and recognized so the oncoming driver doesn't move into your path in the first place. You avoid the split-second decision and the possibility of a crash under braking on a bad surface. So the measures described here should be incorporated into a larger strategy.
Also, it's important to understand that an intersection approach can't always be made crashproof. When speeds are high and the roadway is narrow, exposure cannot be substantially reduced. Improving your visibility to other motorists by maintaining clear sightlines and predictable speed is more effective because if they see you and yield right-of-way, they never become a threat.
But your primary strategy can fail if you encounter the truly clueless. When one of them happens along--and it's not so rare--the additional precaution of an intersection approach that reduces exposure could be a lifesaver.
My conclusions are based in part on a mathematical model described here: Intersection Kinematics (100K PDF).
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