Why Hybrid Cars Make That Weird Humming Noise In Reverse

A hybrid vehicle can be a great choice if your daily drive includes a lot of city miles thanks to relatively high fuel efficiency. Of course, this comes with the question around what happens when your hybrid's high-voltage battery dies. You also may be concerned about the higher upfront cost of a hybrid car. But one item you can scratch off your worry list is the weird noise in reverse that hybrids make. 

Whether you're rocking a Toyota Prius or a Ford Maverick, hybrids are required by law to produce a consistent noise for speeds over 19 mph, going forward and in reverse. Billed as the Pedestrian Safety Enhancement Act of 2010, federal authorities came up with this legislation to address the low noise level of hybrids operating at low speeds. 

Because these types of vehicles can be quieter than cars with a traditional gas-powered engine, artificial sounds are required to alert pedestrians, especially those who are visually impaired, that a car is backing up or slowly approaching. One of the first hybrid cars to feature this alert tone was the Toyota Prius, which could be optionally fitted with a noise-making device in 2010. 

For the initiated, who might mistake odd sounds from a neighbor's hybrid car in reverse as some kind of maintenance-related problem, there is a lot to learn about these kind of vehicles. Like what happens if you don't plug in a hybrid car of the PHEV variety, for example. Or maybe you prefer looking into the truly silent operation of a vehicle from one of the most highly-rated EV brands. As hybrid car sales continue to grow, there are more of these vehicles on the market than ever before.

This makes a warning tone all the more essential for pedestrians and bikers, especially those who are visually impaired and drivers with obstructed views. Fortunately, modern vehicles — including hybrids — possess a number of other safety features, including automatic emergency braking, blind-spot monitoring, and lane departure warnings. These precautionary measures fall under the umbrella of advanced driver-assistance systems, and we look forward to seeing what other risk-reducing car safety measures are heading our way.