Transverse cracks run perpendicular to the pavement centerline (or laydown direction) and are not part of any pavement joints or seams. They are frequently generated by thermal expansion and contraction. Transverse cracking can also occur as a result of a reflection fracture in an underlying layer or hardening bitumen (asphalt binder). Reflection fractures form when asphalt pavement reflects light from its black surface onto itself, causing more intense heat buildup than normal. This can happen during clear days with high temperatures, causing transverse cracks to appear in otherwise smooth pavement. Transverse cracks may be open or closed. Open transverse cracks are visible from both sides of the road while closed-end transverse cracks are only visible from one side. Cracks may also be vertical or nearly horizontal. The depth of transverse cracks depends on several factors such as temperature, moisture content of the soil under the pavement, type of maintenance done on the roadway, etc. Transverse cracks usually range from 1/4 inch to 1 inch deep. However, they may reach deeper levels if water enters the zone where the soil meets the pavement or if excessive load is applied to the pavement. Also, transverse cracks may become deeper over time as the result of vehicle loads being applied to the pavement beyond what it was designed for. Transverse cracks can be problematic because they can lead to structural failure of the pavement. As they get deeper, the risk of injury increases for drivers and riders.