Vehicles of virtually every type and make have been steadily growing over the past ten years. “Entry level” cars by companies like BMW are almost the same size nowadays as a mid-size car from a decade ago. One of the consequences of vehicle sizes expanding is that parking now is harder than ever.

The most obvious vehicle size increase has been in the pickup truck segment, where “small” trucks like the Dodge Dakota now look like giants beside their early predecessors. Full-size trucks have also been expanding, becoming heavier, wider and taller. Toyota too has participated in this growth trend. The Toyota Tundra was originally a mid-size pickup marketed to full-size buyers. Toyota realized a larger vehicle could fit more customers, and as a result, the 2007 Tundra was much bigger than earlier models in almost every dimension.

The downside of bigger vehicles is that parking is now a lot harder than it was before. When driving a new Toyota Tundra, you may notice it’s difficult to tell where the truck begins and ends. As a solution to these new parking woes, vehicle designers have developed a new tool for drivers called “parking assist.”

On most vehicles, “parking assist” is a system of sensors in the front and/or rear bumper that create an audible “beep” when your vehicle gets close to an obstacle. Depending on the system, the beeps will begin when you’re about 6 feet away, and then increase in frequency until you get about 6 inches away, when the beeps will become a continuous tone. This is a great feature - it can really help with parallel parking, as well as warning you if something small (i.e. a fence post, a mailbox, or even a small child) is near your vehicle. But how does it work?

Basically, a set of eyes are mounted in the vehicle’s bumpers. These “eyes”, or special sensors, transmit highly focused sound waves at regular intervals from the bumper. When these sound waves come into contact with a solid object, they reflect back towards the sensor. Since the speed of sound is fairly constant through air, a computer uses the time it took for the reflection to be returned in order to calculate the distance between the bumper and the object. This is exactly the same principle employed by submarines using active sonar underwater, except that water transmits the sound waves much better than air, allowing for better range.

While the system is effective when dealing with stationary objects like parked vehicles, posts and garage doors, the sensors are not quite sensitive enough to pick up smaller objects moving past the sensors. This means that small children, animals, or all-terrain vehicles might not generate a warning beep - or at least not a consistent warning beep. So, while parking assist - aka parking sonar - is definitely a useful tool, it is not a replacement for caution. Drivers must still do their best to ensure that there is no one behind or in front of their vehicle when parking.

High-end luxury cars have started to move on to the next generation of parking assist systems, which use a video camera and complex computer program alongside the sound sensor system. The result is more accurate input to the vehicle, which instead of merely warning drivers close to an object, will actually steer and park the vehicle for them. This is very useful with parallel parking - you just have to let the car control the steering, gas and brake. What interesting and amazing technology we have these days!