Speed limits vary across the EU : from 80 to 100 km/h on road, from 90 to 130 km/h for highways. Saving time is a main motivation for driving always faster. Yet, as speed increases, time saving gains become smaller : switching from 110 to 130 km/h shortens the trip much less than from 70 to 90 km/h. Besides, a temporary high speed is not a guarantee of a high average speed. Sometimes, the opposite is true : lower speed limits can lead to shorter trips ! This has been seen on various urban expressways in French cities.
As an illustration, the French highway corporation APRR has reported 50 % less congestion, and shortened average travel times during peak hours on a part of highway A13 since the implementation of a traffic regulation system that can adjust and decrease speed limits.
Beyond this, speed limits have indisputable benefits : lowering fuel consumption, and in turn environmental impacts (greenhouse gases, local air pollution), lowering noise, less driving stress, etc.