wie fand man raus das man zu schnell fahren kann?

The number of road deaths continued to increase. In 1970 there were around 15 million cars in West Germany and nearly 20,000 traffic deaths. In view of these figures, a further reduction in the rule has now been discussed: a speed limit on the country roads, where at the time the maximum speed was still left to each individual. In 1972, the maximum speed on land roads was set at 100 km/h, and the limit was finally introduced in 1976. This regulation was also strongly discussed again.

https://www.zeit.de/mobilitaet/2019-02/speed limitation-tempolimit-deutsche-autobahnen-debatte-strassenverkehr

https://de.wikipedia.org/wiki/Zul%C3%A4sige_H%C3%B6chstspeed_im_Stra%C3%9Fenverkehr_(Germany)

and for “too fast” you don’t have to find out… just drive faster than the tempolimit. just because it’s on a sign, the car doesn’t suddenly get weaker by itself.