Question on Hazard Perception Tests

hi, thanks for the hazard perception commentary clip, very useful as I'm training to be an ADI, but I'm struggling with the hazard perception element of the theory test. Could you offer me any advice please? I am either clicking too early, so outside the scoring window, or am clicking late so only scoring 3's. I am very concious of clicking too many times as this discounts any score, and have made this mistake during practice. Is the scoring window open when the vehicle being used to film actually starts to make an adjustment? (either speed or direction). Thank you for any pointers.

Reply:

Oh I hate these computerised hazard perception tests, I feel they are so unreal and hard to operate - i have the same kind of trouble as you with the ones I have tried in the past!

One would like to think the scoring window is open even once the host vehicle has begun to deviate, but I suspect from what you say this is not the case (and you can see a certain logic in this, because it means you are now dealing with the hazard, not spotting it in advance).

My best advice would be to go over the system of hazard perception you are using - for example, are you keeping up the scanning; are you starting at the horizon and working forward and constantly re-adjusting the distance of your vision so that you are picking up things well in advance, far off. (This is one of the reasons I hate the computer systems, because you cannot see the detail in the distance. Nor can you adjust your position - both fundamental parts of good hazard perception.)
nik

Is traction control your enemy in the snow?

Traction Control is fitted on many modern cars, designed to help prevent and control skids and loss of traction. It may not however be your best friend in the snow.

The issue that you may face is that when the traction control detects slip at the wheels, it reduces the power to the wheel. (This can be by cutting power at the engine, or on more sophisticated systems by braking the slipping wheel).

On the whole this would seem to be a good thing - when setting off, for example, it reduces slip. If you accelerate it can also control slip. And if the car teeters sideways, then the correction at the wheels is intended to bring it back on track (and generally does. I once tried putting my Saab 93 Aero sideways in the snow using the handbrake - with ESP on I barely got more than 30 degrees out of kilter. With it turned off, I nearly totalled a road sign.)

So why is reduced power to the wheels a bad thing? One word: hills!

Trust me - this is the word of someone who has, in the past, become stranded on hill because he couldn't turn the traction control system off fast enough (a system limitation, I might add). You see, what happens as your car begins to climb a slippery hill is the drive wheels, not surprisingly, begin to slip - especially if the car is front-wheel drive. As they begin to slip the traction control system reduces power. But you're going uphill - so reduced power means you slow down. And if this process continues, before long you can be stationary. Then you might not get going again. 

You might argue that the traction control detects loss of grip, and if there is no grip you can't get up the hill anyway. Well, it's not necessarily true. The traction control system is not able to perfectly measure the co-efficient of friction between the wheels and the snow and also has a necessary characteristic called hysteresis. In simple terms, it's only an approximation- it might not know, for example, that spinning the wheels to dig down through the surface snow might find grip underneath; it will never let you do this.

So, be warned. I don't recommend turning your traction control off in slippery conditions, but be ready to turn it off if you are approaching an upward hill. Check, too, that your car allows you to do this - some cars only allow it when they are below a certain speed. As ever, be prepared.