Neither, I'd rather measure a car as about 13 ft 2 in long.
I'd recommend that you ought to measure a car's length as about 4 m in length as a car 4 km long would be about 2.5 miles long.
As a guide: the longest trains average about 2 km (1.25 miles) long with the longest in the US limited by air brake capability to about 3.7 km long.
The longest ever train consisted of 682 loaded wagons and 8 locomotives evenly placed throughout the train for a total length of 7.353 km (4.568 miles). It was all controlled by one driver.
you would measure a wall in meters
Kilometers
meters
Meters
Meters.
meters
Meters
Neither. By centimeters
Usually, you would use kilometers.
milimeters
if you are talking about how tall you are, meters would be the best choice. for instance if you are 2 meters tall (6ft give or take a bit) that would be like .002 kilometers
A football would be measured in cm. A raisin would be measured in mm A house would be measured in m