Worn-out tires are no good for a car, right? But they can be good for another type of transportation: walking!

In Zimbabwe, and in many other countries, old tires are not thrown away. Instead, craftsmen cut them up and make them into sandals (凉鞋). One of these craftsmen is Casper Mamutse, who runs a small sandal-making business just outside his house.

When Casper first saw a man named Isaac wearing tire sandals, he thought they looked funny. So he asked Issac where he got them. Issac said he had made them himself. Casper decided to buy a pair to make his friends laugh. But his friends didn’t laugh, instead they wanted their own. “Finally, I asked him to teach me how to make tire sandals,” says Casper.

For more than six months, Casper learned how to cut and shape soles (鞋底) from tires. To make the right size, Casper traces a shoe sole on the tire and cuts out a sole. “Cutting a tire with a knife requires as much brains as strength,” he says. “You have to use a lot of power and concentration or else you will cut your finger along with the tire.” After the sole is cut, Casper tears off the soft inside part of the tire and cut it into strips (带状物). He attaches the strips to the sole for “belts”. From one tire, Casper can make about four pairs of sandals for adults or about six pairs for kids.

The Zimbabwe countryside is full of sharp stones. Unless you have thick soles, your shoes can be easily pierced (刺穿). But strong boots are expensive, and many people walk barefoot. But now they can get tire sandals, which are strong enough and much less expensive than leather shoes.

Fedzai, a 10-year-old boy, thinks that what his friends need now are not cars to take them to school, but shoes. “Going to school on foot instead of in a car does not bother me very much,” he says. “After all, we are still moving on tires.”

San Francisco — After years of testing with a human backup driver, General Motor’s Cruise is launching fully driverless cars onto public streets in San Francisco, the most complex urban environment robocars that have been tested, the company announced.

The company said on Wednesday it was deploying (部署) five self-driving vehicles in San Francisco’s Sunset District, an area that bears many of the city’s typical traits: narrow and busy streets, steep inclines (坡度) and fog. Cruise said it was confident enough to launch the driverless trials after five years’ testing.

The company, which began the driverless testing in November, said it plans to expand to other neighborhoods. But the first tests will not put the driverless vehicle fully in control. Instead, the backup driver will be effectively moved to the passenger seat at early trials. Although those operations will not have access to traditional driver controls, they will be able to stop the vehicle if there is an emergency.

Companies in Silicon Valley and elsewhere are working to make driverless vehicles a reality, saying that they will help decrease motor vehicle deaths, which number around 40,000 annually, and allow cheaper ride-hailing (打车) trips by ridding of the need to pay a human driver.

Companies such as Cruise and competitor Zoox have set their sights on San Francisco, seeing the potential reward of conquering a complex urban environment and the country’s second-most populated major city, rather than starting small and gradually making progress.

You’re on the third lap around the car park, there are no open spaces, and you’re already 15 minutes late for your appointment. Right now you’re wishing you could jump out of the car and let it go find its own spot.

Now there’s an app for that. Virtual Valet lets your iPhone tell your car to park without you in it. “You pull up to the roadside, push a button on your smartphone and the car takes care of everything else,” says Aeron Steinfeld, the lead researcher for the project at Carnegie Mellon University in Pittsburgh, Pennsylvania.

To find its own spot, the system uses a sensor suite similar to those found in many luxury cars. This includes a motion sensor that scans for moving cars and pedestrians, and a forward-facing laser rangefinder normally found in adaptive cruise control to determine the distance of objects in front of the car. Information from these sensors is then fed to an onboard computer to plan the vehicle’s course. The user can watch the whole process from his or her phone.

Better still, it will be affordable. The team has spent the last year moving from high-end imaging and processing equipment to less expensive components. In experiments, the vehicle was able to navigate through a crowded parking structure, find an empty spot, and park all on its own. And the greatest appeal of the Virtual Valet Parking App is that it requires no change to existing parking facilities or infrastructure.

For the moment, the only car equipped for control by Virtual Valet is Carnegie Mellon’s modified (改进的) Jeep Wrangler, which the researchers have named NavLab11. But Steinfeld hopes that major car manufacturers will adopt the technology.

It might be more than technology that holds up the show, however. Self-driving cars have been licensed in only three US states — California, Nevada and Florida — and it’s unclear how this app would agree with self-driving laws. Until these questions are settled, your insurance provider might be unwilling to cover a ding from a parking incident.