Future generations of drivers may never know the feel of an engine rumbling through the key as they start their cars.

Automakers are turning away from traditional turn-key ignition switches and installing push-button starters. The new systems are considered safer and more convenient, but could mean the end for traditional keys.

"It is kind of weird that instead of getting a set of keys, it's a fob," said Michael Marchiori, 17, of Grosse Pointe Shores. "There's definitely a much better feeling when you get to feel the car turn on."

Push-button ignitions work via the fob, also known as a "smart key," which allows a driver to keep the device in a pocket, purse or other place when unlocking, locking and starting the vehicle. Antennas or sensors in the car recognize and can communicate with the fob using unique coding.

"The days of keys are numbered," said Dave Sullivan, manager of product analysis for auto researcher AutoPacific. "It's definitely a trend we're continuing to see."

Ward's Auto, an industry-watcher that recently started tracking installation rates of push-button ignitions, reports 25.4 percent, or 4.4 million, 2013 model-year cars and trucks sold had the feature. Installation rates are on track to substantially grow for the 2014 model year.

Push-button ignitions are standard or optional in 72 percent of 2014 cars and trucks in the U.S., according to research site Edmunds.com. That compares to a decade ago, when it was offered on just five cars.

"You can see where automakers are going with it," said Edmunds senior analyst Jessica Caldwell, adding new generations of car buyers "thrive on convenience."

Many automakers are beginning to offer push-button ignitions as a standard feature.

Chrysler Group's newest vehicles — the 2015 200, 2015 Charger and 2015 Challenger — come standard with push-button systems. Only about a dozen Chrysler models, primarily large trucks and SUVs, come with traditional metal keys.

Ford Motor Co. reports that all models except its Transit and Transit Connect vans/wagons and super-duty and commercial trucks are offered with push-button ignitions.

General Motors Co. CEO Mary Barra, in the wake of the ignition switch recall of 2.59 million vehicles that has been linked to at least 36 deaths, told Congress last spring that GM may discontinue using turn-key ignitions: "The push-button start is something we're evaluating putting across the portfolio," she told a House Energy and Commerce subcommittee.

GM spokeswoman Jennie Ecclestone said the Detroit automaker continues to evaluate which vehicles are best suited for keyless starting. She said GM offers keyless ignition on 20 of its 2015 models, including nine models standard.

Analysts, however, say that GM's ignition switch woes aren't the cause of the industry's change. Availability of the feature increased before the recalls, and it's more a convenience than a safety measure.

"Once the customers get used to it, it almost becomes a requirement on the car," said David Fischer Jr., general manager of dealer group Suburban Collection, adding the technology is a gateway for others like remote start and keyless entry.

However, push-button ignitions aren't fault-free. Drawbacks include steep replacement costs of fobs, the inconvenience of fobs dying with no way to start the car — and even potentially fatal consequences when drivers don't understand how to turn it off.

During Toyota Motor Corp.'s unintended acceleration problems in the late 2000s, there were reports of customers not knowing how to turn off Toyota and Lexus vehicles with push-button ignitions in the event of unintended acceleration.

Following an August 2009 crash that killed four, Toyota told drivers to "firmly and steadily push the button for at least three seconds to turn off the engine. Do NOT tap the engine start/stop button."

Separately, an incident involving a push-button start in a Lexus in 2009 killed 79-year-old Ernest Codelia Jr. and left his companion, Mary Rivera, brain-damaged.

Rivera parked her car in a ground-floor garage attached to the couple's New York residence and accidentally left the engine running. The next day, Rivera was found unconscious and Codelia dead. The cause of death was carbon monoxide poisoning.

Lawsuits against Toyota from that incident as well as from a separate case were settled out of court for undisclosed amounts earlier this year, according to lawyer Noah Kushlefsky, who filed the lawsuits.

"You no longer have the tactical clue of (keys to tell you), 'I forgot to put it in park' or the car is still running," he said. "It's a human factors issue."

The National Highway Traffic Safety Administration has received hundreds of complaints about push-button technology, from roll-aways to vehicles not starting correctly.

In 2011, the watchdog agency proposed standardizing keyless ignition controls, requiring audible warnings for drivers who fail to use the button properly. A final ruling is expected early next year.

Many automakers have addressed concerns themselves. Chrysler, for example, has "Safe Hold," which activates the electronic parking brake if the driver leaves the car running in gear and tries to exit. And engines turn off after the ignition button is pushed three times or held down.

Kelley Blue Book senior analyst Karl Brauer predicts future vehicles will use scanners that identify a driver's fingerprint to start a car.

Staff writers Melissa Burden, Michael Martinez and David Shepardson contributed.