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A PHYSICIST WRITES . . .

(July 2014)

Regular readers may remember that last year I changed my 1997 (manual) Toyota Corolla for a 2010 automatic VW Golf. Actually, it was quite a surprise to discover how many areas of a car had become automated during the 13 years: the auto-gearbox was the least of it (almost)! So Iíve been thinking about some of the systems that govern themselves, in a modern vehicle (or in mine anyway).

Let us start with the lighting: the Golf has daytime-running lights that come on automatically with the ignition. Thatís fine with me Ė Iíve checked them from in front, and they donít dazzle (unlike some). Though I notice that the bulbs each contain two filaments, the other one being for the full-beam headlight (whereas on the Corolla and previous cars, it was the dipped and full-beam filaments that shared a bulb). This makes me worry Ė slightly Ė about whether the filaments will withstand the extra heat from each other if I signal with the headlights (in the daytime) for more than a moment!

Also, it does seem a waste for the day-lights to be shining when the car is not running but parked on the driveway, while Iím simply investigating some other function that requires the ignition to be on ... for example, the lane-change flashing. You may know what I mean by this: just a nudge of the direction-indicator lever causes the lights on the appropriate side to show three times (and then stop).

Now firstly, I would say that three flashes arenít necessarily enough for indicating clearly (to drivers who may not be concentrating on your car) that you are about to change lanes. So I often find Iím holding or leaving the lever down, to indicate for longer. But more annoyingly, if you touch the lever accidentally thereís nothing you can do to stop the three flashes. My ownerís manual says that it is possible to switch the function off permanently, but VW Reading told me it wasnít.

[Update: a recall notice required me to take the car in (Iíll tell you the full story another day), and I asked VW to look into the lane-change flashing at the same time. Afterwards, again they said that nothing could be changed Ė yet as I drove away I found the three automatic flashes had somehow become two! Some improvement at least...]

The main light-switch on the Golf has an Auto position, which (Iím almost ashamed to say) I make use of all the time. I can safely rely on it to bring on the front and rear lights, in place of the daytime ones, as soon as dusk approaches. Whatís slightly unsettling is that this also happens when I drive under bridges, through tunnels or into overhanging greenery.

This must be a puzzle to some approaching and following drivers, though curiously I donít seem to notice other vehicles flicking from daytime lights to headlights and then back, as they go through. Of course in bright rain or fog I still have to remember to switch the lights properly On. And not forget to put them back to Auto when the weather clears.

The windscreen wipers too have a mind of their own! By which I mean an Auto position Ė and the way it works is clever: Iíve found out that behind the upper windscreen is a source of infra-red light and a detector of it. When raindrops land on the glass, the reflection back from them brings the wipers into action. The cleverness of the system lies in its not being affected by daylight or by reflection from the windscreen itself.

I can adjust the sensitivity of detection so that the wipers will sweep just about often enough whatever the amount of rain. But hereís an oddity: according to the manual (not to mention common sense) when the wipers start the headlights ought to come on, for a few minutes at least, but they donít. According to VW this is merely one more discrepancy between the manual and the vehicle...

Letís look next at cruise control, which would appear to be another useful automatic facility. You are probably familiar with how it operates: when first switched on, it holds the car to the current speed (except that the brakes wonít be applied Ė unless you have adaptive cruise control and are catching up with another vehicle). You can also nudge the set speed higher or lower. As soon as you touch the brake pedal the control disconnects, until you press a switch for it to resume (going back up to the set speed).

Now correct me if Iím wrong, but if my Golf had a manual gear-box, and I needed to change gear when in cruise-control mode, this would similarly disconnect the control. So it seems I am rather better off in my car, because with the gear-changes happening automatically I can cruise up hill and down dale for as long as I like! And at any set speed at all, unlike in a manual-gear car (again correct me if Iím wrong).

Anyway, Iíve mainly been using my cruise control for keeping the car to whatever the speed limit is, from 70 mph down to 20, on clear roads Ė I instinctively sensed danger in leaving it in charge when there was traffic around, or other hazards ... but hold on: the reality is more serious. I have just now come across a report of a French investigation which revealed (by use of a driving simulator) that when drivers had their cruise control switched on, there was a distinct drop in their general attentiveness.

This showed up in a reduced ability to hold to a good straight line within a lane, poorer judgment when overtaking, a longer reaction time (by an average of one second!) to any sudden event, and a greater level of tiredness as reported by the subjects. And most of these effects worsened as the journey continued.

So: far from cruise control enabling you to concentrate on driving tasks other than watching your speed, as you might think, what it does is to blunt probably all your driving skills and also increase the risk that you will actually nod off. Something tells me that I wonít be using this facility again.

Lastly, letís dip into some alphabet soup: ABS, ASR, BAS, EDL, ESP, TCS and XDL are all referred to in the Brakes section of my Golf manual. Iíve looked each of them up elsewhere, for my information and yours: ABS = Anti-lock Brake System, which most cars possess these days to stop the wheels locking up, so that they can supply maximum braking force, given the conditions. ASR = Anti-Slip Regulation and is the same (I think) as TCS = Traction Control System, which reduces the engine output if wheel-spin occurs.

BAS = Brake Assist System which, when you hit the brake pedal, detects the move and applies the brakes even faster than you can. EDL = Electronic Differential Lock, which senses when a front wheel has lost traction and brakes it, giving the other wheel the drive-power. ESP = Electronic Stabilization Programme, designed to cut the risk of skidding (somehow). XDL seems to be like EDL, but more advanced.

What an array of automatic braking systems! But do any or all of these letter-triplets really apply to my Golf? Certainly an ABS light comes on before I start the car (and so does EPC, whatever that stands for). Thereís also a button for disabling the ESP, though Iím not sure why should I want to. But otherwise I have no idea which of the listed alphabeticals are actually helping to keep me safer on the road. The FAQs in the manual tell me nothing. Yet you would think that finding out ought to be as easy as ABC...

Peter Soul

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