Listed in Highway Safety
It’s not uncommon for concerned residents—especially those with young children—to contact their local highway superintendent with a simple request: “Can we get a speed bump on our street to slow traffic down?” It’s an understandable concern. Everyone wants safer streets, especially in residential neighborhoods where kids might be playing nearby. But when the posted speed limit is already 30 MPH—which is usually the lowest speed permitted by state law outside of a designated school zone—adding speed bumps isn’t just inadvisable. It’s actually unsafe.
Speed bumps are engineered for roads with speeds of 15 to 25 MPH, where it is perfectly safe to hit the bump or speed table at the posted speed limit. They’re designed to jolt a vehicle if it goes too fast, encouraging drivers to slow down significantly—especially in places like private driveways, parking lots, and very low-speed local roads. If a driver is going the proper, they likely shouldn't need to decrease speed when approaching the bump. Speed bumps are intended to communicate to a speeding driving that they need to slow down, not jostle every vehicle that passes through. But on a road posted at 30 MPH, the dynamics change.
Hitting a speed bump at or near 30 MPH can cause a vehicle to bounce or lose control, especially for smaller vehicles or those with poor suspension. It also creates a serious risk for motorcycles, bicycles, and emergency response vehicles. Even if drivers do see the bump in time to slow down, sudden braking can increase the chance of rear-end collisions.
From the perspective of a parent watching cars zip past their home, a speed bump seems like an easy fix. But the reality is that physical traffic calming devices like speed bumps can cause more harm than good when placed on roads designed and posted for 30 MPH or higher. They don’t just risk vehicle damage—they can actually endanger the very people they’re meant to protect.
Imagine a delivery van hitting a speed bump at 30 MPH and losing control, or a fire truck being delayed because of multiple bumps on a route. These scenarios aren’t just hypothetical—they’re why engineering standards and traffic regulations exist.
Better Alternatives for Traffic Calming
If speeding is a persistent problem, there are safer and more effective ways to address it:
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Targeted enforcement: Temporary or permanent radar speed signs and occasional police presence can make a strong impression on habitual speeders.
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Narrowing visual cues: Pavement markings or curb bump-outs can help psychologically narrow the road, which naturally encourages slower driving.
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Public awareness: Educating neighbors about speed limits and encouraging community-wide safe driving habits can go a long way.
While the instinct to protect children and slow traffic is always valid, speed bumps on 30 MPH roads just aren’t the right tool. They can create more hazards than they solve. Highway superintendents aren’t ignoring safety concerns—they’re following sound engineering standards designed to keep everyone safe, including the people behind the wheel.
If you're concerned about speeding on your street, reach out to your highway department and ask about appropriate traffic calming measures. There are better, safer solutions than speed bumps.
Also read: The Fallacy of Children at Play Signs.