If this technology becomes common place, what is the future of speed bumps?
It seems as if speed bumps are a rather questionable approach to traffic calming, as larger vehicles (which should be a priority for calming) are less affected.
We use chicanes (of a sort) and single lane bottlenecks in the UK. Forcing the vehicle to turn is a pretty easy way to get people to slow down and people complain less because it's friendlier on their suspension. In my home town there's one road that was clearly experimental? where the whole (one way) road gently zigzags for maybe 500m.
I've never understood speed bumps as a concept. Almost every car has at least 4in of travel, so you can hit them at significant speed and not damage anything. In fact the faster you hit them or the more load you're carrying the better the suspension handles it because you open up the high speed compression valves. If there's no one around and it's an empty remote rural access road I'll often hit them at 30mph+ with no issue. Rolling over them at a slower speed where your shocks stay uncompressed forces your whole car to go up and then down again, instead of absorbing the energy in the shocks.
> so you can hit them at significant speed and not damage anything.
That’s the point. They’re not supposed to damage the car. They’re supposed to be a little uncomfortable if you’re going too fast.
It’s more reminder than a physical stopper.
> In fact the faster you hit them or the more load you're carrying the better the suspension handles it because you open up the high speed compression valves.
This is a case of knowing just enough about a topic to be dangerous.
Entering the higher shaft velocity part of the damper curve doesn’t mean the suspension is handling it “better”. The high speed behavior of the valving simply means the damping forces aren’t increasing linearly with shaft velocity. They trade extra travel for reduced peak forces.
Make no mistake, though. The faster you go, the higher the forces. The high speed valving (if the OEM dampers are even digressive) isn’t changing that.
If the speed bump is tall enough and the bump stops get completely compressed you could bottom out the damper, which is not good for it.
> I'll often hit them at 30mph+ with no issue.
Just because nothing immediately breaks doesn’t mean you’re reducing the life of the OEM dampers. Repeated high speed impacts and will shorten the life. Getting the wheels bumped up into the range where you’re compressed bump stops transfers a lot of energy into the bushings and other components.
> Rolling over them at a slower speed where your shocks stay uncompressed forces your whole car to go up and then down again, instead of absorbing the energy in the shocks.
That’s the ideal way to do it. This is better than the sudden sharp impact of high speed crossing. You’re not doing your car any favors by driving quickly over speed bumps. Fortunately for you, OEM replacement dampers aren’t too expensive but replacing prematurely worn bushings is kind of a pain.
>This is a case of knowing just enough about a topic to be dangerous.
>Entering the higher shaft velocity part of the damper curve doesn’t mean the suspension is handling it “better”. The high speed behavior of the valving simply means the damping forces aren’t increasing linearly with shaft velocity. They trade extra travel for reduced peak forces.
>If the speed bump is tall enough and the bump stops get completely compressed you could bottom out the damper, which is not good for it.
Oh the irony!
In practice none of the suspension parts on any car are in any danger until you run out of up travel and determining where the deflection will happen becomes a competition between the air in your tire and the suspension components.
No automotive suspension is designed so that the damper bottoms out. You'll have an external bump stop somewhere, sometimes on the damper shaft, in any case the damper itself isn't bottoming out, you'd know, probably even hear it specifically if it did.
Regularly traveling rough roads, hitting rumble strips, comically out of round tires or anything else that creates oscillation is going to be way, way, way worse for component longevity (dampers, bushings, etc) than a hard bump from time to time.
You're not going to hit your bump stops until you max out the travel, which a 4in speed bump is likely not doing unless you're in a fairly low car.
> The faster you go, the higher the forces.
The higher the forces into the dampers, yes, but the whole point is that if you're in the right section of the damping curve they spread it out and turn most of it into heat. With well tuned suspension that means lower peak force on the rest of the car, which means less rattling of every single part other than the unsprung bits.
> If the speed bump is tall enough
Those are a rare exception on pubic roads. All the points you make are about pushing your car beyond max travel, which obviously will start to break things. I'm talking only about bumps below your max travel, which I argue you can hit at significant speed with minimal wear to anything sprung.
> This is a case of knowing just enough about a topic to be dangerous.
I mean I do race off road competitively so I've had plenty of experience testing these assumptions and witnessing real-world wear on my components as a result. If you ride washerboards all day in high heat you'll see plenty of blown shock seals, but with well tuned suspension a single speed bump at 30mph wont harm a thing on the average car. It just makes a "thud" that sounds like damage to people, and I guess that's a good deterrent.
Properly built speed bumps are most comfortable to traverse at posted speed, but are very well felt when you're speeding. In my experience they build them well in Northern Europe, less so in Eastern.
Not in any parts of northern Europe where I drive. You are usually (exceptions exist) supposed to reduce speed very much below posted speed limit before passing the bump. For example, posted speed is 50kmh but speed bump is designed to be crossed at no more than 20kmh. If you drive a less comfort oriented car, make that 5kmh instead of 20kmh.
I drive mainly in Norway but hadn't noticed any difference in Sweden or Denmark. If you drive the posted speed here you can count that your wheels won't be knocked off. If you have to reduce speed (say around schools or near poor visibility crossing) then there is a sign for different speed, as simple as that.
You won't lose your wheels going at the posted limit, if it is a 30kmh road. For comfort you probably do want to reduce down to 15-20 in an average car.
If you encounter a warning sign for speedbumps on a 50kmh or 70kmh road you better start braking if you dont't fancy getting airborne.
There are some weird deadlocks in Swedish road regulations that make it unreasonable difficult to change the speed limit in some situations. They sometimes work around that by actively making it impossible to drive the posted limit.
OK, maybe that's a thing in Sweden after all, certainly not here. Just drove a whole bunch of speed bumps on the way to work today anywhere from 30km/h to 50. You'll never encounter a speed bump in a 70 km/h zone here.
Allow me to cordially invite you to test out a speed bump set up at exactly 51.201580°N, 16.972742°E. It's not visible in Street View yet, which adds to the surprise.
>I've never understood speed bumps as a concept. Almost every car has at least 4in of travel, so you can hit them at significant speed and not damage anything.
They only work because the average consumer doesn't know this.
Speed bumps are already almost meaningless with modern suspensions. Next time you have a rental car hit a few at speed and you might be surprised how well an average car handles it.
Speed bumps are much rougher in my idiot monster truck than they are on my Mercedes station wagon, idiot monster truck spring rates and damping are engineered to tow heavy loads/carry heavy payloads so especially when unloaded speed bumps are quite jarring compared to a passenger car.
Except for the fact that the in the average case the monster truck is probably being driven by someone who'll full send it (which minimizes the bump) and the Mercedes is being driven by someone who'll inevitably crawl over it at 2mph.
But yeah, swap the average drivers and the Mercedes is gonna do way better.
Just hit them significantly faster, it'll do the same thing as going slow with a heavy load. There's a reason the faster you ride motocross the harsher you tune your spring and damping rates.
My riding skill improved so much the day I fully grokked "lean back and twist the throttle" to handle obstacles (I did it by accident and thought I was going to die)
what's the reason? it surely isn't ride smoothness, it's control.
similar to a race car -- you don't compensate the speed with damping and spring rates in order to maximize a smooth ride , you do it to more quickly transfer the movement energy OUT of your car, into the ground and traction patch so that the car can remain dynamic for the next force.
this does not equate to ride quality, most race cars (and bikes) are bone-shakers.
ride smoothness in the medium frequency range = control. if you're bouncing all over then you're weighting and de-weighting constantly, which is terrible for control.
high performance cars are mostly bone shakers at slow speeds when not in their ideal operating range. at high speeds they should level on top of it all, just watch a rally truck go over dunes or the video of an F1 wheel well stabilized to the frame of the car. sure you have low-frequency high-g-force weight transfer during acceleration/deceleration, and you have high frequency signal from the road texture, but medium frequency parking-lot-speedbump-style bouncing should not be happening at all or you're going to lose the race.
My first thought. It's the ultimate American invention, something to let you fly straight over the speed bumps people have installed to keep their streets safe, neatly tying up the infatuation with car culture with a complete disdain for all life outside the car.
It seems as if speed bumps are a rather questionable approach to traffic calming, as larger vehicles (which should be a priority for calming) are less affected.