Why should riders avoid metal grates, painted lines, and manhole covers?

Riders should avoid metal grates, painted lines, and manhole covers primarily because they can be slippery, particularly in wet conditions. When rain or moisture accumulates on these surfaces, they become slick and can result in a loss of traction. This loss of grip is particularly dangerous for motorcycles, which have a smaller contact patch with the road compared to cars. Riding over slippery surfaces can lead to loss of control and increase the risk of accidents.

In addition to this primary reason, it's important to be aware that while some surfaces can be hard to see, especially in certain lighting conditions, the slipperiness of these surfaces is a more immediate safety concern for riders. Riders must also remember that metal grates and painted lines might not be the same traffic hazards to cars as they are for motorcycles, due to the different dynamics involved in riding. Lastly, issues like tire wear from these surfaces are generally less of a concern compared to the impact on safety when riding over them in adverse conditions. Understanding these factors can help riders make safer decisions on the road.