Speed breakers are safety devices that keep check on the fast-moving traffic. But what does the speed breaker do when the vehicle is already slow approaching. Is there any better breaking system design approach which keeps the fast-moving vehicles in check but eases the travel of the slow-moving vehicles?
Shallow, wide speed bumps are easy fore slow traffic while offering more or less the same impact as narrow, high speed bumps. Because the impulse force remains the same for fast speed.
They are having an unintended benefit: because of change in the subtended angle from the driver's eye to the bumper, they signal the distance better by changing the perspective as the approaching car get closer.
Several companies have developed speed bumps / speed breakers that "disappear" when driven over below a set speed. My favourite designs are those that use non-Newtonian fluids. See this random paper for example.
As far as I can remember you can make a non-Newtonian fluid using water and lots of corn starch. Poke your finger in slowly and it will feel little resistance. Poke quickly and the fluid will "lock up". A search on YouTube should find plenty of examples. Practical designs will have to work over a wide range of temperatures and survive abuse by heavy vehicles running at high speed. They won't be using corn starch!
A common approach in residential areas where I live is to occasionally move a lane a car width towards the edge of the road every few thousand feet then back, with a small median and curb between the lanes. Essentially creating a slalom run. Probably not ideal in congested urban areas as it uses 1.5 times the space for the road but useful in suburban/rural housing developments where there is excess land. No problem navigating the turns at 35 mph but almost impossible at 80 (for cars at least).
What you are talking about is called traffic easing or calming. The best solutions include the design of the road and everything around it. We build big wide roads and are somehow surprised that people drive fast on them. Speed bumps are a part of a solution when we can't get the other elements right. There are several types, and the uses are dependent on what we're trying to achieve exactly.