2018 Mercedes Benz E400 reads and reacts to speed limit signs on the fly

Image credit: Mercedes Benz

On the road to fully autonomous driving, there are a few milestones that give us some hope. Cars like the Volvo S90 that can adjust speed for the car in front of you on the highway and a Tesla Model S that can go hands-free for short periods have already set the bar. 

This year, Cadillac challenged the Tesla throne with Super Cruise, a feature on the 2018 Cadillac CT6 that lets you drive without touching the steering wheel, even for several hours. 

Another milestone? A feature on the 2018 Mercedes Benz E400 called Active Speed Limit Assist. 

It’s not brand new, and you can find it on other Mercedes models like the S-Class and several BMW models, but it’s a sign of things to come – adaptive intelligence, machine learning, image recognition, and real-time mapping on major highways. 

2018 Mercedes Benz E400 reads road signs and adjusts accordingly (Credit: Mercedes Benz)

2018 Mercedes Benz E400 reads road signs and adjusts accordingly (Credit: Mercedes Benz)

As you drive, the E400 will adjust the speed you are driving to match the post limit. (You have to enable the feature in the main display; to activate, just use cruise control.) 

It’s an exciting innovation for a few reasons. One is that you don’t have to think about the speed limit (say what you will at this point about going 5 mph over the limit, which many drivers feel is an acceptable risk). 

You can pay attention to other things, like the sports-car on your bumper. Of course, you should always be aware of your speed.

More than anything, it shows how cars are becoming more aware of the roadway, the posted limits, and eventually could sense imminent dangers long before you see them yourself.

With Active Speed Limit Assist, it feels like an AI has taken over (Credit: Mercedes Benz)

With Active Speed Limit Assist, it feels like an AI has taken over (Credit: Mercedes Benz)

In testing it, there’s a feeling that an AI has taken over, one that adjusts automatically. On a four-lane highway, the E400 surged gently forward at times before we even realized the limit had changed. 

This can help in situations where you are driving slowly and don’t realize why everyone is looking at you. In one case, a jump from an area with stoplights with a speed limit of only 55 mph suddenly changed over to 70 mph.

Road awareness

Mercedes doesn’t do the abrupt speed change common on other vehicles that finally have adaptive cruise control, like the 2018 Toyota Prius Prime. Instead, it’s gradual. 

During a longer test outside of a major city, there were times when we forgot the E400 was even changing speeds. It’s easy to see how future cars will also read conditions like construction zones, icy pavement, an accident, and other problems reported either to traffic centers or that the car can identify.

Still, Active Speed Limit Assist isn’t perfect. It worked for us only at normal highways speeds; in a traffic jam on a lonely country road with poor lane markings, it wasn’t available. 

Another specification to consider? The optional Premium 3 package adds $10,200 (about £7,320 / AU$13,080)  to the $58,900 (about £42,274 / AU$75,538) base price. You’re driving forward into the future, but not at Toyota Prius prices.

On The Road is TechRadar's regular look at the futuristic tech in today's hottest cars. John Brandon, a journalist who's been writing about cars for 12 years, puts a new car and its cutting-edge tech through the paces every week. One goal: To find out which new technologies will lead us to fully autonomous vehicles.

John Brandon

John Brandon has covered gadgets and cars for the past 12 years having published over 12,000 articles and tested nearly 8,000 products. He's nothing if not prolific. Before starting his writing career, he led an Information Design practice at a large consumer electronics retailer in the US. His hobbies include deep sea exploration, complaining about the weather, and engineering a vast multiverse conspiracy.