Speed limits are one of the most important safety measures in place to prevent auto accidents. Observing the speed limit reduces your vehicle’s stopping distance and provides more time for you to react to signs that an accident might happen. The speed limit also encourages uniform traffic flow, ensuring that all drivers have a chance to merge and change lanes safely. Likewise, the speed limit protects at-risk parties like pedestrians and individuals on bicycles and motorcycles.
Braking Distance
As your car accelerates, it requires significantly more energy to overcome things like wind and rolling resistance. The air pressure that drives wind resistance follows a power law, and that means that 50% more acceleration requires 100% more energy.
When you brake, the energy that keeps your car moving doesn’t instantly dissipate. If your car has 50% more energy because you’re speeding, then you will need twice the distance to come to a stop when you apply the brakes.
Consider a common scenario where a driver is going 30 mph because it’s the speed limit and someone coming up behind them is going 45 mph. If the safe driver applies the brakes in time to stop just short of another vehicle’s bumper, the trailing driver will plow into them at 30 mph. This is because they need twice the distance to stop and have only dissipated half their vehicle’s energy. If the 30-mph driver needed perhaps 45 feet to stop, the 45-mph driver would need 90 feet.
Reaction Time
Humans do not react immediately to stimuli, no matter how attentive they are. The average human takes more than 0.2 seconds to react, and some people take nearly 0.5 seconds. This is just the time to process the visual stimulus and react. They make take longer to apply their vehicle’s brake.
Notably, speed limit calculations take this into account. This is why you see speed limits of 25 or 30 mph on many suburban roads with foot traffic and nearby families.
Traffic Flow
Reaction time also affects traffic flow. You aren’t just dealing with the reaction times of two potential drivers who might be a part of an accident in many cases. When people are driving on expressways, they may need time to determine when to execute lane shits and then make the maneuver. The same goes for finding and hitting an exit.
Traffic flow is a complex system involving many drivers who all have different reaction times. Likewise, the quality of their vehicles’ brake systems also varies significantly. The speed limit ensures that these individuals can safely maintain the traffic flow.
Protecting At-Risk Parties
Pedestrians, bicyclists and motorcyclists all face greater injury risks because their mass relative to a car isn’t sufficient to protect them. The law accounts for these differences and sets local speed limits according to how exposed such at-risk parties are in a specific environment.
Drive Safely
Excessive speeding can lead to tickets, fines, points on your driver’s license and increased insurance premiums. But aside from those inconveniences, speeding can cause dangerous situations for yourself and other road users.
The speed limit protects you and other drivers from potentially catastrophic automotive accidents. Observe the speed limit in all situations by staying aware of signage that indicates changes. Stay attentive in all circumstances and drive defensively when you see other motorists who are speeding. The life you save could be your own or that of a loved one.