TOKYO/FRANKFURT, Germany (Reuters) -- At the recent Frankfurt Auto Show, Ford Motor Co. unveiled a new feature that lets drivers preset their car to go at or just above the speed limit. In-car cameras and software read and react to road signs, speeding the car up or slowing it down. Active Speed Limiter is available on select models in Europe, but not, ironically, in the U.S., Ford's home country, where road signs come in different shapes and sizes, and are often obscured by shrubbery.

So it goes on the road to the self-driving, or autonomous, car: a journey of, well, stops and starts that most experts say will take a couple of decades to complete.

Meanwhile, advances in so-called semiautonomy -- features that help handle tricky or tiresome driving situations but still require a driver's oversight -- have sparked a high-tech automotive arms race, with car companies vying to launch the most advanced features.

Automakers hope semiautonomous features will, over time, help drivers and regulators get over fears of riding in vehicles that accelerate, steer and stop themselves, making potentially life-or-death judgments. Shorter term, car companies want these features to make driving more convenient and cars more profitable.

"People like features that make driving easier, safer and more fun," says Joseph Vitale Jr., who heads global automotive consulting for Deloitte Touche Tohmatsu. "The question is what customers will pay for them."

Ford's Active Speed Limiter comes at 560 euros ($602.78), and it's too soon to tell how popular it will be.

Among the biggest winners for now are the companies that produce electronic sensors, cameras and software that make self-driving features possible. The growing list includes the high-tech units of traditional automotive suppliers such as Germany's Continental AG and Israel's Mobileye Vision Technologies, as well as consumer-technology giants Alphabet Inc., Apple Inc., Samsung Electronics Co. Ltd. and Sony Corp., among others.

At Silicon Valley's Nvidia Corp., for example, video games remain the biggest market, but automotive revenue is the fastest-growing segment. "We're in well over 8 million cars on the road today and will be in more than 30 million in the next three to four years," says Jen-Hsun Huang, Nvidia's CEO and president. "Future cars will sense and understand the world moving around them."

'Doing Crazy Things'

A big step in that direction was the traffic-jam-assistance feature on the 2014 Mercedes-Benz S-Class. Now available on more Mercedes models, the Intelligent Drive system allows the car to drive itself at low speeds in traffic jams, freeing the driver from constant braking.

BMW, Honda Motor Co., Hyundai Motor Co. and others have or will soon introduce similar features.

Silicon Valley's Tesla Motors Inc. recently broke new ground by downloading "autopilot" features to its newer models, just as software updates are downloaded to smartphones and tablets. Autopilot basically drives the car itself, but Tesla warns drivers not to relinquish control entirely. On a recent investor call, Tesla CEO Elon Musk said he had seen some "fairly crazy videos on YouTube" of Tesla owners driving hands-free with autopilot, and added: "This is not good. We will be putting some additional constraints on when autopilot can be activated, to minimize the possibility of people doing crazy things with it."

Bells And Whistles

For consumers, getting their first car with semiautomated features can be both exciting and daunting, especially among those who haven't bought news car in years.

"I had no idea this sort of thing was out there," says Mark Goldsmith, a Tokyo-area TV news writer. "I'd been driving a 15-year-old Jeep, which only had cruise control that you constantly had to adjust, so all these new features are a novelty." Goldsmith recently traded the Jeep for a 2015 Volvo with a mouthful of a name, the V40 T5 R-design, and a handful of semiautomated driving features.

Those include adaptive cruise control, distance warning, a blind-spot information system, a driver-alert system, lane-keeping aid, road-sign information, an anti-skid system and parking assist. Combined, they add close to $1,000 to the car's total price of nearly $31,000. While Goldsmith says he has yet to test all the automated features, he says the suite of functions was "definitely" a factor that helped sell he and his wife on the car.

But to other drivers, such as Kirstin Houser, a communications and events manager in Frankfurt, mastering how to use all the buttons, switches and toggles to activate the automated drive functions on her family car, a 2015 Mercedes E-Klasse Kombi, was a time-consuming process that required "relearn(ing) how to drive.” She says: "There are just too many bells and whistles on the steering column, either to push, pull, scroll, hold down, release, etc. By the time I remember which one to use, there's already a row of cars behind me honking to park my car. Safe driving, and also understanding the general mechanics of a car, are so engrained in the way we drive that it's hard to separate that and allow our car to make those judgments."

Target 2020

Ford recently added automated straight-in, so-called perpendicular parking on some models. While developing the feature, company engineers found that cars could self-park in places so tight that drivers couldn't pull out of them. They reworked the software to add pull-out capability to Active Park Assist, which is priced at $395 in America and 350 euros in Europe.

BMW's new flagship 7 Series sedan has a remote self-parking feature that allows the car to park itself with nobody inside. Drivers stop, hop out, push a button on the key fob, and the car takes over.

Alphabet’s Google is holding discussions with at least half a dozen car companies with aims of launching its self-driving car system by 2020. That same year, Japan's Big Three -- Toyota, Nissan Motor Co. and Honda -- are targeting the Tokyo Summer Olympic Games to launch and showcase cars that will largely handle themselves in city traffic, but not entirely.

"We maintain our expectation that drivers will remain in control of their cars in 2020," Moritaka Yoshida, Toyota's chief safety technology officer, said recently at a demonstration of the company's latest automated driving technology. Nonetheless, the company's Lexus GS450 SX models equipped with cameras, radar and laser sensors changed lanes and merged smoothly in heavy traffic, without help from the driver.

The 2020 Olympics could become a venue for automotive as well as athletic competition, and not just among traditional car companies.

Tokyo-based Robot Taxi plans to bypass semiautonomy and deploy 3,000 self-driving taxis that athletes, VIPs and tourists can summon by smartphone apps to ferry to and from venues. "It's not about the car," company' Chairman Hisashi Taniguchi told Reuters. "We're going to generate revenue from supplying self-driving vehicles as a service, and collecting user fees. It's all about the app, and how many people use it."

($1=0.9290 euros; $1=122.9700 yen)

(Reporting by Paul Ingrassia and Naomi Tajitsu; Editing by Ian Geoghegan)