5 Reasons Why Cars Are Allowed To Go So Fast

Car going too fast on the interstate highway

If you think about it, cars are pretty scary. Most cars can go upwards of 140mph, but they’re forced to go 65mph on the highway. Meanwhile, highways in Germany don’t have speed limits. That begs the question: why are cars allowed to go so fast?

Highways have higher speed limits because that’s what today’s cars can handle. With more safety features, smoother roads, and impatient drivers, it makes sense that you’ll be going 50 to 85mph on the open road. Cars themselves can go so much faster mostly due to the overengineering and gearing involved. In Germany, a lot of training and impressive engineering explain the lack of speed limits on the autobahn.

I did some research when putting together this guide. I’ll first talk all about cars in general, speed, and safety. In this article, I’ll answer the big questions along the way. Let’s start off with some safety talk.

The Relation Between Higher Speeds and Safety

Before answering this question, I want to talk about how speed and safety are connected. Safety is the only reason why roads have legally-enforced top speeds in the first place. Here’s why.

Longer Stopping Distances

The faster you go, the longer it takes you to stop. In physics, this is called inertia and momentum, and there are a few equations that calculate the total stopping distance.

Car stopping distance when hitting applying the brakes illustration

If you’re going 20mph, your total stopping distance is around 40 feet. If you’re going 40mph, your total stopping distance is around 118 feet.

At 70mph, you can expect a stopping distance of 315 feet. As you can see, the difference is pretty dramatic. Simply doubling your speed results in a distance that’s nearly three times longer.

Reaction Time

Part of that difference has to do with reaction time. Humans have a certain amount of time that they need to process information before they have a physical reaction. If someone tells you to blink, it will take a fraction of a second before you understand what they say, think about blinking, send the signal, then finally blink.

Classic Red Porsche 911 driving fast with the rear blurred to give a sense of motion
Porsche 911

During this reaction time behind the wheel of your car, the vehicle is still moving. If you’re going 70mph, that reaction time is calculated to be about 70 feet. Your car moves another 70 feet before you even start braking.

More Unpredictability

With everyone going roughly the same speed, you can pretty much predict what other drivers are going to do. If speed limits disappear, then there’s no telling what to expect. Someone might just randomly floor it and start going 150mph then blow past everyone without warning.

Traffic Lights Become Scarier

Imagine approaching a yellow light at 200mph. Slamming on your brakes could cause you to fishtail, so you decide to blow through the light. At the same time, the opposing traffic light turns green, and someone blows through the intersection. Suddenly you’re looking at a fatal accident for everyone involved.

Car sudden braking at a traffic light to avoid a collision with the vehicle in front

The solution is to have stoplights that stay red for much longer — maybe even 10 times longer. Instead of one light turning red as the other begins to turn green, there needs to be a long delay. This slows down traffic dramatically and will probably result in people going through red lights on purpose.

Not All Cars Can Go Very Fast

So, let’s say that speed limits go away, and everyone can go as fast as possible. The country is still riddled with cars that can’t actually go that fast. Smart cars and box trucks struggle to even maintain the speed limit on a highway.

Suddenly, these cars are at risk. All it takes is an impatient driver to not see them, and they’ll get rear-ended at high speeds.

Going fast is great as long as everyone goes fast. With cars that physically can’t keep up, there are roadblocks across the country.

How I’ll Break Down This Question

I understand that the question of why cars are allowed to go so fast can be broken down into a few different interpretations. I’ll do my best to talk through each interpretation.

You’ll notice a few different sections as you keep reading. First, I’ll talk about why car speed limits are currently so high. 65 miles per hour is fast enough to do serious damage, and a lot of people consider that fast. In other words, why do cars go so fast?

US American road sign speed limit of 65 MPH in the desert

Next, I’ll describe why cars can physically drive so much faster than even the highest speed limit in the country. In that interpretation, I’ll explain why cars can go so fast.

Finally, I’ll take a look at Germany’s autobahn in an effort to explain why cars can go so much faster elsewhere.

5 Reasons Why Cars Are Allowed to Go So Fast

If you think about it, a car going on highway speeds is really fast. If you’re driving through Texas highway 130, the posted speed limit is 85mph. Even with modern safety features, that’s a lethal speed in a lot of accidents.

So, why are vehicles allowed to go much faster than they have before in the past?

1. Roads are Build Better

In the old day, speed limits were abysmally low because a lot of the roads were unpaved. Going too fast on a dirt road will always result in losing control and spinning out.

Aerial view of the interstate highway traffic in the city of Los Angeles

Over the centuries, roads started being built better — a lot better. Sure, you’ll still find a ton of potholes, especially in more populous and colder areas. That doesn’t take away from the fact that the holes routinely get filled, roads get repaved, and (in general) roads across the country are well-made.

2. The Engines Can Take it

Another thing that changed over time is how well a car’s engine performs. Even an old beater truck can go highway speeds without the engine failing.

Since cars are able to go so fast, why not let them? It would be a different story if pistons were being blown every week on the highway.

3. Brakes are Getting More Efficient

In addition, stopping times are getting more impressive. The big issue with going faster is that it takes you longer to stop. If someone gets in front of you with their vehicle or an animal happens to walk onto the street, you need to slow your car down quickly.

Blue car in the service station with the wheel removed exposing the car disc brake and rotor on front driver side

With modern brakes, this is possible. Since we can stop quicker, we are able to drive faster.

4. People Favor Arrival Times Over Safety Implications

Even with a posted speed limit, speeding tickets are handed out in the tens of millions annually across the country. This is further proof that people would rather arrive quicker than drive safer.

The simple fact is that there’s no way to uphold a 25mph speed limit across the country. People will easily go triple that without batting an eyelash.

I’m guilty of this, too. I want to get to my destination quicker, and that’s why I’m okay going 65mph down the highway instead of 25mph.

5. Added Sensors Make Things Safer

Another development in the automotive world is the sensors available. Even an entry-level 2022 vehicle will have a ton of safety features and sensors. Your car will warn you if you need to brake, it’ll check your blind spots for you, and it might even keep you in your lane.

Car braking assist sensor emergency braking assist (EBA) to avoid collision on modern cars

This is another reason why it makes sense for cars to go so fast on the road. Every day, driving at high speeds is safer thanks to these added sensors.

Why Cars Can Drive Faster Than Speed Limits

Next, let me talk about the purpose behind cars going faster than local speed limits. In reality, there’s nothing stopping every car manufacturer from maxing their cars at 85mph. Meanwhile, cars like Koenigsegg’s Jesko can go upwards of 330mph. What’s the point?

Speed is Exponential Based on Engine Size

The underlying science is based on the relationship between speed and engine size. The rule of thumb is that an engine needs to be 8 times more powerful to achieve a top speed 2 times higher.

Close up of a BMW performance engine with dual intakes

By dropping faster engines, cars get much better performance on the road. Things like 0-60 times will improve, along with cornering ability and track times.

When the top speed is increased, it typically means that the car has better acceleration. Yes, these two variables aren’t technically connected, but they both have to do with the power of the engine in the vehicle.

Some Cars Actually Have Electronic Limiters

If you get a Chevy Cruze, you’ll notice that the car stops revving and accelerating after 108mph. Why such a random number? There’s an electronic limiter inside the car’s computer.

The limiter physically limits the car from going any faster. You can get up to 108 and then stomp on the gas pedal and nothing will change.

Realistically, these limiters can be dropped down to 85mph across the country since that’s the highest posted speed limit in America. They aren’t for other reasons described in this article.

In the Case of Emergencies

Let’s say your friend got stabbed and needs to be rushed to the hospital. Instead of waiting for an ambulance, you might jump in the car and speed there. This is illegal and dangerous, and I would never recommend doing it.

A person POV driving a car very fast on the interstate at night

Still, the fact that cars can go so much faster than the speed limit means that you can get to the hospital quicker. It could be lifesaving to get there quicker. I can think of a dozen different emergencies in which you’d benefit from going faster than the speed limit.

It’s a Matter of Overengineering

If you want to boil it all down, it’s a matter of overengineering. A manufacturer wants their car to go 65mph reliably for life. How do they design that? They create a car that can go 140mph reliably. All of a sudden, 65mph is a cakewalk.

Gearing for Fuel Economy and Safety

Another part of the design process revolves around the gearing in the transmission. To create seamless shifts all the way up the box, the top speed needs to be boosted. If a car had a top speed of 65mph, your car would be redlining the entire time you’re on the highway.

Close up of the RPM tachometer gauge on the speedometer dash instrument cluster going 2,000 RPM

Instead, you can go 65mph while cruising comfortably at 2,000 RPM.

At the same time, gearing minimizes how much fuel you use. Turning a massive gear takes more energy to go at the same speed as a much smaller gear. That’s why transmissions step through a series of increasingly-large gears.

Why Cars Can Go Faster on the Autobahn

In this breakdown, I’ll talk about why cars are allowed to go so much faster in other countries. More specifically, I’ll be looking at the autobahn. If you didn’t know, this is a series of highways over in Germany that doesn’t have speed limits.

Most of the stretches have 3 or 4 lanes going in either direction. They follow a rule where the slowest cars go in the right lane, and the fastest go in the left lane. Some parts of the autobahn have a speed limit, but most of it is unrestricted.

Autobahn A5 interstate highway in Germany with roadsigns near the Frankfurt airport

The government suggests going about 80mph, but then they shrug their shoulders and say “or however fast your Porsche goes”.

Why can you legally go 160mph without getting a ticket?

The Roads are Better Maintained

Above everything else, German engineering allows cars to go so fast. Road engineers in Germany have a lot of respect, and designing these highways is no easy task. They create impossibly level, smooth, and slowly rounding roads that allow drivers to go so fast.

I’ve personally been on the autobahn, and the road is so smooth you feel like you’re gliding. On American highways, you can almost feel the road in certain cars. Every bump and grain of the asphalt can lead to disaster at high speeds. In Germany, all you feel is the smoothness.

The Drivers Go Through Lots of Training

Believe it or not, German drivers have to go through extensive training before they get their license. A buddy of mine explained that he needed to log 25 hours of professional driving courses and then spend a few thousand bucks for his driver’s license.

A male instructor teaching a female driver near parking cones at a car driving course

Comparatively, an American driver can roll out of bed and just get their license. The worst-case scenario is that you take a quick 30-minute test that requires no practicing and you get a lenient test supervisor that gives you a license.

With this extra German training, drivers are more knowledgeable about how to drive. I’m not saying that we don’t know how-to, but a typical German driver seems much more impressive behind the wheel.

Germany Has Fewer Drivers

A big speed inhibitor is road traffic. With America’s 235 million drivers on the road, traffic is an everyday obstacle. Compare that to Germany’s 48 million cars. With only 20% of the American fleet on the streets, they can get away with driving faster without as much traffic.

Germany is also 28 times smaller in terms of the area of the country. I would argue that most of America’s highways see very less traffic since the majority of the population is focused near the major cities. The same logic still holds, regardless of the size difference.

The Rules are Widely Understood (and Actually Followed)

The shocking thing about driving on the autobahn is how well the drivers actually follow the rules. I mentioned that the law dictates that slower cars should be in the right lane, but they actually do it.

If you drive up and down I-95 along the east coast of America, you’ll find that every lane is about equally occupied. People go in whatever lane they want, and they go at whatever speed they want. There’s always an old guy going 20mph under the speed limit in the left lane, and it’s just a part of daily life.

Califronia expressway near San Francisco showing the left express lane of the interstate highway

On the autobahn, this doesn’t happen. Most of the cars are in the right-most lanes, and only the very fast cars are on the left.

If a driver sees a fast car approaching them, they’ll get over and let the fast car pass. If a driver wants someone to move out of their way, they’ll turn on their left turn signal and the car in front will actually move over. It’s hard to believe.

Conclusion

Now you know everything about cars and why they’re allowed to go so fast. I hope I answered all your questions on this topic. If you have any comments or further questions, leave a comment below.

For more of your car questions answered, check out the rest of my blog. I also have a list of highly recommended car products that you should take a look at.

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Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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