The noun "speed" can be both countable and uncountable.
Meaning: how fast something or someone moves
Example sentence: Most people hate those machines the police use on the side of the road to measure speed.
Meaning: a particular speed
Example sentence: Many young men love the excitement they feel when riding a motorbike at dangerous speeds.
Test your understanding:
- He didn't start reducing the car's speed until he got to the city.
- He kept driving at a very high speed until he got to the city.