Gears

Gears allow faster travel without overheating.  They are simply levers arranged around wheels of different sizes, in a gearbox.  ​ In a "manual" car, you need to change between gears.  You don't need a certain gear to deal with a certain feature on the road. The car may suggest changing up or down to make the engine more efficient, but it can't see what you can see ahead. So, your CONTEXT defines your safe SPEED, and your speed defines the best GEAR.

In a manual car, you'll need to use the clutch before you change gear. That disconnects the engine from pushing the wheels round. (Think how a short-legged runner would need to disconnect their feet from the ground first, before they could "change to longer legs" to stride ahead faster).

​A gear-change should be made at  (1)  the right speed,  (2)  when your left hand's free,  (3)  if it's calm outside, (4)  in a smooth, easy movement.

An automatic car changes gear for you, depending on how much power is needed from the engine to move. Electric cars have no gears at all: they simply move by magnetic repulsion.