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Avoiding diesel and other slippery spills
Some years back, there was a long discussion on the problems of diesel on one of my favourite forums. My first introduction to the slippery nature of fuels spilled on the road came soon after I'd taken my 125 up to London. I stopped at a pedestrian crossing, three bikes came flying past me, turned right and promptly formation-crashed. As I pulled away, the 125 span the back wheel. Even that early on in my riding career I knew that wasn't quite right and took the corner rather more slowly than the other bikes. A truck was parked halfway up the hill with a split tank and some fireman throwing bags of sand around it. The slick reached right down the hill to where the bikes had crashed. That was a while ago, and on purely observational evidence, it seems to me that fuel spills are much less common than when I was a courier. Moreover, evidence from police accident investigations suggests that despite the popular belief that oil and diesel cause bike crashes, the real crash numbers are low. That might be why most of the correspondants who had mates "who have crashed on diesel", surprisingly few actually put up their hands and said "I've crashed myself".
Nevertheless, it's as well to be on the alert. As with all hazards, the first thing to consider is where we might find it, secondly how to spot it, and thirdly and to have some idea of what to do if we do spot ANY oil, diesel or petrol spill - they are ALL slippery.
Where might we find diesel and petrol (it's slippery too) spilled on the road? The obvious answer is where vans, trucks and buses start with full tanks. And that means ports, industrial estates and bus depots, particularly in the morning. Leaving aside the random spills from a split tank, or from the van that had taken off its sump on high kerb round a traffic-calming 'pinch point' (it didn't get far but left quite a slick for half a mile), keep an eye open where vehicles change direction - corners, junctions and particularly roundabouts are likely problem areas.
Combine a roundabout with exits marked INDUSTRIAL ESTATE and we should be on alert. Back when I was a trainer in Lydd, my homeward route took me round the Ashford ring road, which has a dozen industrial estates round it. Just as I was slowing for a right turn at one of the roundabouts, a guy on an R1 flew past signalling right as well. Knee out, he vanished around the back of the island but never reappeared. Going round rather more cautiously, I avoided the big streak of diesel and stopped to lend a hand. Rider unhurt but bike rather sad, having flipped over after sliding into the kerb. I left him arranging a van ride home. If we're apply the 'stop in the distance we can see to be clear' rule, don't forget it applies to road surface too.
Another good rule-of-thumb is that diesel spotted on one corner will probably reappear on the next. Another courier followed me carefully round one left-hander leading out of one London square as we both avoided the diesel. He overtook me, and promptly crashed on the left-hander leading into the next square just few hundred metres further on. As I stopped to help him untangle the bike from the railings, he said: "I didn't expect diesel on that bend too".
Err, right. So where did you expect it?
Most spills either come from overflows on over-filled tanks (much rarer now) or when drivers forget to put the filler cap on. Don't laugh - I forgot to put the bike filler cap on once, because the tank bag covered it. A lapful of fuel reminded me, but the driver won't know. The fuel is likely to be be spilled outwards so look for it on the outside of the lane - near the centre line on a left-hander or the kerb on a right-hander. But don't forget a oncoming vehicle could slosh it our side of the centre line on a right-hander too.
Watching the surface is one reason for not trailing a vehicle ahead too close. If we see temporary slippery road signs or even police SLOW triangles, take care - it could be a spillage or even accident ahead, and there may well be a slippery cocktail of detergent, diesel, engine oil and antifreeze on the road.
See if you can spot the spill. In the rain, oil produces the familiar rainbow effect. It looks scary because the rain washes the oil right over the road, but in fact the rainbow effect is produced by a layer just one molecule thick. A single drop of oil can produce a big circular rainbow patch. It's slippery but not lethal - the tyres will cut down to the surface. But if we see the rainbow right across the road, then it's a bigger spill. Try to see which way the rainbow's being washed - the source is probably in the other direction and that's the area to keep clear of.
Unfortunately, in the dry, there's no warning rainbow. The best advice I can give you is that fresh oil and diesel is very wet-looking and very shiny. It's looks like 'very wet water' for want of a better description. A big diesel spill in the dry can often be smelled. So use your nose. A dulled black streak is almost certainly an old spill, and unlikely to be particularly slippery. But it's worth knowing that if it rains, old spills can be 'reactivated', particularly by a short shower after a long dry spell.
Don't forget petrol can also be spilled. It's just as slippery as diesel but harder to see - it looks like water. Whenever possible, keep clear of any unusual wet-looking patches.
Interestingly, in that forum discussion, there was little useful advice, beyond declarations that "it'll will have you off if you hit it" statements.
Ideally, we do want to stay off it if possible. It's just a matter of having the speed and lean angle in hand to change line and direction. But sometimes we simply have cross a spill. It's straightforward enough if we can avoid leaning and braking (the usual instinct) as we cross it, and instead keep the bike as upright as possible. For that reason if I find a spill mid-corner, I tend to steer INSIDE it, even if that means sacrificing my view round the bend. Why? I may have to cross it. If I'm on the inside, I can pick the machine up and cross it upright, before leaning over again back on clean tarmac. But if I'm on the outside and need to cross it, I actually need to increase my lean angle. Not a good plan. And don't forget that the tyres will take a moment to clean off - don't bang the bike straight over on its side, but ease it over.
Look ahead, think ahead, plan ahead, and oil and diesel should be no more than a minor - if potentially dangerous - irritant.
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