Traction is a concern anytime you are on a motorcycle. Some part of your mind should be addressing it whenever you ride. It is a primary issue when you are braking or cornering, a moderate concern while you are accelerating, and still of a little interest when you are riding straight at a steady speed. It can even be an issue when you stop and put your foot down.
Actually, it isn't traction you are thinking about. Your mind is worrying about all those things that can eliminate traction—water, oil, coolant, diesel fuel, gasoline, sand, dirt, plasticized sealants, ice and tree sap, to name a few.
Your first line of detection is normally your eyes, but sometimes slippery stuff can be deceiving. Occasionally an oil slick looks like a tar patch. Sand can look like a slightly different pavement composition. Diesel fuel or coolant can appear as just a slight, nearly invisible sheen on the road.
Shade can hide a slippery hazard or actually create it. After a dewy night in our local mountains, the road sometimes stays wet and glazed until the sun reaches it. However, during the winter months, the low sun may never dry off some corners, and even in the afternoon riding into a shaded corner can produce a slick surprise. If it gets cold enough after the sun goes down, that leftover moisture can freeze. (Using one of those key-chain thermometers as a zipper pull on your jacket can provide information about whether temperatures are near freezing.) Even on a warm, dry day, a shaded corner can be hazardous, especially if you are coming from bright sun. The shade can hide sand or dirt, and I have seen more than one rider crash in a dark dusty corner.
Experience can help you learn the signs of slick surprises, but there are things you can do to help. For one thing, avoid polarized glasses, which can hide the shine of something slippery. Use your nose to smell spilled fuel, coolant and oil. (If you don't know what coolant, oil and diesel fuel smell like, you should learn.) If you smell any of these things, you slow down and move away from the part of the road you suspect to be contaminated. Many times they are not visible.
Lubricants and other automotive fluids are normally the slickest stuff you'll encounter on the road. Cars and trucks are the usual source of spilled fluids, though they used to leak a lot more. We were always advised to avoid the center of the road, where the oil usually fell, especially in heavy traffic areas and major intersections. That's still good advice, especially when it's wet. Heavy traffic areas that are covered and protected from the elements—tunnels and toll booths, for example—are almost always slippery when it rains. The rain doesn't fall directly on the road surface to wash the oil away but instead drops off the wet vehicles that pass through, giving you that super-slick oil-on-water mixture. The curving tunnel at the west end of U.S. Interstate 10 where it becomes Pacific Coast Highway, which adds an off-camber turn to the equation, is a classic and scary example. Most riders will eventually encounter a toll booth on a rainy day, and if they don't remember how slick they can be, they probably will when they put their foot down or at least when they accelerate away.
In corners, fuel or oil is likely to get thrown to the outside, so if you smell or suspect a spill, you can usually avoid it by staying to the inside. Staying to the inside also gives you more room to straighten up without running out of lane. On the other hand, moving to the outside as you enter a corner and staying there until you can see all the way through the turn allows you to look farther down the road and gives you more time and distance to adjust for any potential hazards. This latter approach is the one usually recommended, and if you enter the corner with some speed margin to allow you to tighten your line if needed, it gives you the most options.
What do you do if you see a strip of oil in a corner you will have to cross? Slow down and tighten your arc before you reach it and cross it as upright as possible with no brakes and the throttle in neutral. The oil will stay on your tires for a few rotations, so continue with caution, avoiding hard turns or braking. Of course, unless you have encountered one of those oil traps someone deliberately dumped in the middle of a corner (increasingly common in Southern California), the line of fuel or oil is likely to simply follow the bend of the corner all the way through. You will have to decide whether to ride inside or outside of it. In a right-hand bend, staying inside is usually the best idea, especially if you can see it goes all the way through the corner. In a left-hander, staying clear of the line of spilled fluid might place you too close to the oncoming lane, so you'll have to decide if there is enough room to stay safely inside of it. In any event, the best approach is to slow down so your need for traction is reduced and you can straighten up to cross the slick as needed.
Lots of things land on roads and make them slippery, and some things are there permanently—manhole covers, metal bridge gratings, paint, railroad tracks, cattle guards and those plasticized sealants some road-maintenance agencies use to seal cracks. They offer little traction when dry and almost none when wet—and many of these metal items are the first places where ice forms on wet, cold days.
While some of these metal components could probably be designed to provide better traction, those plasticized crack sealants are clearly the work of some motorcycle-hating devil. While most tar strips are slightly slippery, the newer composites offer all the traction of the inside of an alligator's nose. Sometimes you can avoid them, but other times they spread over a corner and seem to cover more surface than the regular pavement. The only thing to do in that case, especially when it's wet, is slow down and call or write the local road department.
"Go soothingly on the greasy mud, for therein lies the skid demon." That remark has been attributed to everything from Asian road signs and motorcycle manuals to Mark Twain. Whoever said it, it is good advice for motorcyclists who think the demon may be lying in wait. Slow down, straighten up and don't accelerate or brake any more than you absolutely have to, and he'll probably let you go.