As you travel down the runway you may feel small bumps, this is from the runway surface and the runway centerline lights. You may also hear or feel a slight vibration from the plane's wheels as they spin up to speed. The takeoff roll down the runway is normally about 20 seconds.

Bumpiness during takeoff is usually caused by mechanical turbulence or convective currents near the ground. Because the air near the Earth's surface is disrupted by buildings, trees, and terrain, it becomes "choppy," much like water flowing over rocks in a stream. Additionally, as the sun heats the ground, warm air rises in uneven "thermals," creating pockets of different densities that the plane must fly through. Another factor is wake turbulence; if another large aircraft took off just before you, it leaves behind powerful "wingtip vortices" (invisible mini-tornadoes) that can jolt your plane as you follow the same path. Pilots are trained to maintain a specific "climb gradient" to get above this surface-level instability as quickly as possible, which is why the ride usually smooths out once you pass through the first few thousand feet of the atmosphere.