Interior shot of 2015 Dodge Ram 1500 clearly shows the unusual rotary gear selector on the centre stack, to the right of the steering wheel. File photo: Fiat Chrysler Auto

Washington DC – American road safety officials have launched an investigation into about a million Dodge Ram pickup trucks and SUVs prompted by complaints by some owners that the vehicles rolled away and crashed after being parked.

The issues being investigated by the National Highway Traffic Safety Administration are similar the one cited in the June death in Los Angeles of Russian-born actor Anton Yelchin of the recent "Star Trek" movies.

Fiat Chrysler Automobiles said it was cooperating with the government investigation covering the 2013-2016 model year Ram 1500 pickup truck and 2014-2016 Dodge Durango SUV, after the NHTSA said it had received reports from owners of 25 crashes and nine injuries alleging vehicle roll-away.

The agency's investigation could lead it to order a recall if the vehicles are found to be unsafe. In the meantime, the agency and Fiat Chrysler have urged drivers to use the parking brake, in addition to placing the transmission into park, before leaving their cars.

The models under investigation have an electronic rotary gear selector control, which is not the same as the shifter that Fiat Chrysler recalled earlier in 2016 for roll-away issues.

More than 1.1 million Dodge Chargers, Chrysler 300s and Jeep Grand Cherokees worldwide were recalled in April because they could roll away after drivers exited, thinking they had put them in park, a problem that has been linked to at least 68 injuries, 266 crashes and 308 reports of property damage.

Confusing design

The NHTSA blamed the recall on a confusing shifter design that resulted in higher error rates by drivers during attempted shifts to park.

Fiat Chrysler's recall fix was a software upgrade that automatically shifts the vehicles into park in certain circumstances, and it said on Tuesday that 53 percent of the vehicles had already been upgraded with the new software. It has also changed the design of the shifter for future models, to make it similar to a standard mechanical shifter.

Yelchin, 27, was killed when his recalled 2015 Jeep Grand Cherokee rolled backward in the steep driveway of his Los Angeles home and pinned him against a brick wall and a fence. In August his parents sued Fiat Chrysler for negligence and product liability claims in California.

US regulators have investigated a number of roll-away issues in recent years.

On Tuesday the NHTSA also opened an investigation into 39 000 2012-2014 Land Rover Evoques and 2013 Jaguar XFs after seven complaints of vehicles rolling away and four injuries were reported. Like the Fiat Chrysler vehicles under investigation, they have rotary gear selector controls.

A spokesman for Jaguar Land Rover said it was cooperating with the investigation.

Industry analyst Michelle Krebs said the move away from traditional gear shifters by an increasing number of carmakers had left many drivers confused.

"We need to educate customers about how it works," she said. "Also, if you're going to reinvent something that people are very familiar with, you'd better make sure it works perfectly."

In 2012 Honda recalled 871 000 vehicles that could roll away after the ignition key has been removed, saying a component in the ignition interlock could become damaged or worn, enabling the key to be removed even if the vehicle's shift lever hadn't been moved into park.

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