TOTW: Treat morning shadows like oil slicks

The riding tips on these pages are my personal opinion about matters related to motorcycle riding. They are not the official position of any organization, and are for your consideration only. They are not hard and fast rules, they should not necessarily be applied in all circumstances, and they should not be applied without thinking. Always use your judgement and take all current safety factors into account while riding. You are responsible for your riding, not anyone else (especially me). These tips were originally published by a motorcycle riding course, called “Tip of the Week” (the reason for the TOTW in the titles).

What’s the problem?

In early morning or late evening, you will sometimes find yourself riding on a road where nearby trees are casting scattered shadows across the pavement. This situation can cause rapid and extreme changes of lightning and contrast as you move back and forth between sun and shadow. It can be difficult to adjust to the changing lighting, and the dark shadows can hide hazards on the road surface. This is especially problematic in the morning, because, in addition to hiding hazards, shadows on the roadway can also cause hazards by delaying the evaporation of frost or dew.

Especially early or late in the riding season, you may be surprised to find frost or even ice on the roadway well into the morning if deep shadow prevents the sun from heating the pavement. We have even encountered snow on roads, weeks after it should have disappeared, in areas where heavy overhang prevents the sun from ever striking the pavement.

Solution

If there might be a hazard in an area where your visibility is impaired, it is safest to behave as though there is a hazard there. Especially in the morning, treat shadows on the roadway like any low-friction hazard (e.g., an oil slick). Avoid the hazard if you safely can, and drive over it properly if you cannot avoid it.

Like any hazard, it’s best to avoid it if it can be done safely. Perhaps you can change your lane position, or your path through a curve, to keep your tires on sunlit pavement. Be on guard against target fixation — look at the sunlit safe roadway, not at the shadow. However, do not jeopardize your safety to avoid hitting a shadow. Stay in your lane and, especially, stay away from the inside edge, as oncoming traffic may also encounter friction problems and strike you.

If you must drive over a morning shadow, behave as though you know it is slippery. If your speed is excessive, slow down before you reach the shadow so you will not be braking on the unknown surface. If the shadow is in a curve, pick a very conservative path that minimizes your lean angle and the traction demands on your tires. Avoid, if possible, any sudden control changes while on the shadow, and make any necessary changes very smoothly.

Morning shadows are a double threat. They may cause frost or dew to linger on the roadway, and they help conceal any hazard that is there. Use extra caution: a surprise in the morning can ruin your whole day.


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