What speed do speed bumps go on?
Speed Zones and Speed Humps
Speed zones are often taken for granted and until a problem arises, most people pay little attention to the theory behind them. The following information will help you understand how speed zones are established, and what they can and cannot do.
Speed Zone Misconceptions
When traffic problems occur, concerned citizens frequently ask why we don’t lower the speed limit. There are widely held misconceptions that speed limit signs will slow the speed of traffic, reduce accidents and increase safety. Most drivers drive at a speed that they consider to be comfortable, regardless of the posted speed limit. «Before and after studies have shown that there are no significant changes in average vehicle speeds following the posting of new or revised speed limits.
All fifty states base their speed regulations on the Basic Speed Law: «No person shall drive a vehicle at a speed greater than is reasonable or prudent nd in no event at a speed which endangers the safety of persons or property.»
Under California law, the maximum speed limit in urban areas is 55 MPH. All other speed limits are called prima facie limits, which are considered by law to be safe and prudent under normal conditions. Certain prima facie limits are established by State law and include the 25 MPH speed limit in business and residential districts, the 15 MPH speed limit in alleys, and at intersections and railroad crossings, where visibility is very limited. These prima facie speed limits may be enforced without being posted.
Speed limit between 25 and 55 MPH are established on the basis of traffic and engineering surveys (California Vehicle Code — Section 627). These surveys include an analysis of roadway conditions, accident records and a sampling of the prevailing speed of traffic. A safe and reasonable limit is set at or below the speed at which 85% of the drivers drive.
Traffic flowing at a uniform speed results in increased safety and fewer accidents. Drivers are less impatient, pass less often, and tailgate less, which reduces both head-on and rear-end collisions.
The posting of the appropriate speed limit simplifies the job of traffic officers, since most of the traffic is voluntarily moving at the posted speed. Blatant speeders are easily spotted, safe drivers are not penalized, and traffic officers aren’t asked to enforce unrealistic and arbitrary speed limits.
Speeding on residential streets is a common complaint reported by concerned citizens. Speed humps are often requested because they are perceived as a quick and effective solution to speeding. Research has shown, however, that speed humps are not always an effective or safe traffic control device.
What are Speed Humps?
On public streets speed humps are 12 ft. long by 3 in. high ridges of pavement placed across a roadway that theoretically force cars to slow down as they pass over them. They are intended to be uncomfortable to drive over if crossed over to quickly.
Are Speed Humps Safe?
Several tests throughout the world on speed humps have raised questions about their safety and effectiveness. Test results indicate:
- Speed humps do not significantly reduce vehicle speeds once the vehicle has left the speed hump. In fact, the discomfort and shock sometimes decrease as vehicle speeds increase.
- Speed humps may present a potential hazard to all vehicles and particularly to bicyclists, motorcyclists and emergency vehicles, i.e. police cars, fire trucks and ambulances.
- Speed humps cannot be designed to meet the specifications for all types of vehicles because of the wide variety of handling and ride characteristics.
- Traffic volumes on streets adjacent to streets where the humps are located often increase when drivers try to avoid the speed humps.
- Speed humps increase noise levels 10 to 20 decibels when wheels hit the pavement. Increased noise is particularly bothersome in residential areas.
Speed humps are not recognized by the State of California as an official traffic control device. Injuries caused by speed humps may result in significant additional liability for the City. Results of various studies have raised concern about the potential dangers of speed humps.
For these reasons, the City of Huntington Beach does not use speed humps on public streets.
If you have questions, requests or suggestions concerning traffic, please call the Traffic Engineering Division at (714) 536-5431.
Did you know?
Solar energy has been used for over 2700 years. In 700 BC, glass lenses were used to make fire by magnifying the sun’s rays. Learn more about solar.
City of Huntington Beach
Public Works Department
2000 Main Street
Huntington Beach, CA
Phone: (714) 536-5431
Fax: (714) 374-1573
What If? 2: Additional Serious Scientific Answers to Absurd Hypothetical Questions is out! Order here!
How fast can you hit a speed bump while driving and live?
First, a disclaimer: After reading this article, don’t try to drive over speed bumps at high speeds. Here are some reasons:
• You could hit and kill someone.
• It can destroy your tires, suspension, and potentially your entire car.
• Have you read any of the other articles on this blog?
If that’s not enough, here are some quotes from medical journals on spinal injury from speed bumps:
Examination of the thoracolumbar X-ray and computed tomography displayed compression fractures in four patients . Posterior instrumentation was applied . All patients recovered well except for the one with cervical fracture.  Speed bump–induced spinal column injury
Incorporation of the buttocks with realistic properties diminished the first vertical natural frequency from ~12 to 5.5 Hz, in agreement with the literature.  Source: The 2nd American Conference on Human Vibration.
(That last one isn’t directly related to speed bump injuries, but I wanted to include it anyway.)
Regular little speed bumps probably won’t kill you
Speed bumps are designed to make drivers to slow down. Going over a typical speed bump at 5 miles per hour  Like anyone with a physics background, I do all my calculations in SI units, but I’ve gotten too many US speeding tickets to write this article in anything but miles per hour; it’s just been burned into my brain. Sorry! results in a gentle bounce, while hitting one at 20 delivers a sizable jolt. It’s natural to assume that hitting a speed bump at 60 would deliver a proportionally larger jolt, but it probably wouldn’t.
As those quotes attest, it’s true that people are occasionally injured by speed bumps. However, nearly all of those injuries happen to a very specific category of people: Those sitting in hard seats in the backs of buses, riding on poorly-maintained roads.
When you’re driving a car, the two main things protecting you from bumps in the road are the tires and the suspension. No matter how fast you hit a speed bump, unless the bump is particularly large, enough of the jolt will be absorbed by these two systems that you probably won’t be hurt.
Absorbing the shock won’t necessarily be good for those systems. In the case of the tires, they may absorb it by exploding.  Citation: Just Google «hit a curb at 60». If the bump is large enough, it may permanently damage a lot of important parts of the car.
The typical speed bump is between three and four inches tall. That’s also about how thick an average tire’s cushion is (the separation between the bottom of the rims and the ground).  Citation: There are cars everywhere. Go outside with a ruler and check. This means that if a car hits a small speed bump, the rim won’t actually touch the bump; the tire will just be compressed.
The typical sedan has a top speed of around 120 miles per hour. Hitting a speed bump at that speed would, in one way or another, probably result in losing control of the car and crashing.  At high speeds, you can easily lose control even without hitting a bump. Joey Huneycutt’s 220 mph crash left his Camaro a burned-out hulk. However, the jolt itself probably wouldn’t be fatal.
If you hit a larger speed bump—like a speed hump or speed table—your car might not fare so well.  Youtube: Speed bump in Dubai + flying Gallardo
How fast would you have to go to definitely die?
Let’s consider what would happen if a car went were going faster than its top speed.
The average modern car is limited to a top speed of around 120 mph, and the fastest can go about 200.  The Bentley Continental Flying Spur has a top speed of 199.64 miles per hour.
While most passenger cars have some kind of artificial speed limits imposed by the engine computer, the ultimate physical limit to a car’s top speed comes from air resistance. This type of drag increases up with the square of speed; at some point, a car doesn’t have enough engine power to push through the air any faster.
If you did force a sedan to go faster than its top speed—perhaps by re-using the magical accelerator from the relativistic baseball—the speed bump would be the least of your problems.
Cars generate lift. The air flowing around a car exerts all kinds of forces on it.
The lift forces are relatively minor at normal highway speeds, but at higher speeds they become substantial.
In a Formula One car equipped with airfoils, this force pushes downward, holding the car against the track. In a sedan, they lift it up.  Parker, Barry R.. «Aerodynamic Design.» In The Isaac Newton school of driving: physics and your car. Baltimore, MD: Johns Hopkins University Press, 2003. 155.
Among NASCAR fans, there’s frequently talk of a 200-mph «liftoff speed» if the car starts to spin.  The Myth of the 200-mph «Lift-Off Speed» Other branches of auto racing have seen spectacular  Youtube: Porsche 911 GT2 (or GT1) crash backflip crashes  Youtube: Mercedes CLR-GTR Le Mans Flip when the aerodynamics don’t work out as planned.
The bottom line is that at somewhere in the range of 150-300 mph, a typical sedan will lift off the ground, tumble, and crash . before you even hit the speed bump.
If you kept the car from taking off, the force of the wind at those speeds would strip away the the hood, side panels, and windows. At higher speeds, the car itself would be disassembled, or even burn up like a spacecraft reentering the atmosphere.
What’s the ultimate limit?
In the state of Pennsylvania, drivers may have $2 added to their speeding ticket for every mile per hour by which they break the speed limit.  NHTSA, Summary of State Speed Laws, 2007
Therefore, if you drove a car over a Philadelphia speed bump at 90% of the speed of light, in addition to destroying the city .
. you could expect a speeding ticket of $1.14 billion.