Seattle is giving bike sharing another shot. Two shots, actually. Hundreds of bikes, which are owned and operated by a pair of competing companies, are showing up on city sidewalks this week.

“Let’s see what happens,” said Mary Jo Porter as she selected a new Lime Bike using an app on her smartphone in downtown Seattle.

She’s among the first riders to try out the system. Nearby, an orange Spin bike waited for its next customer.

Lime and Spin are each distributing 500 bicycles in the coming weeks in an attempt to see if commuters will pay a dollar for a 30-minute ride.

But wait, didn't Seattle try bike sharing, and didn't it eventually fail?

Yes -- that was Pronto, the city-sponsored system which vanished earlier this year after struggling with low ridership and other problems.

Lime and Spin are different.

First, they're run by private companies. The city of Seattle just issues a permit, allowing them to do business here.

Spin and Lime Bike don't rely on docking stations as Pronto did. Riders can leave the new bikes on any public sidewalk or city bike rack, as long as they aren't blocking driveways, entryways, bus stops, and the like.

Users don't even need to lock the wheels to anything. They secure themselves.

“I think the fact that you can leave it wherever you need to leave it, that's a lot easier than having to go to a station every time,” said Fraser Black, who inspected a Spin bike in Pioneer Square, Tuesday.

Cyclists still need to wear a helmet, which is required by law in King County Pronto provided them, but Spin and Lime don't, so riders have to bring their own.

The new bike systems are part of a city pilot program. The Seattle Department of Transportation will review the performance of Lime and Spin in December, and then decide if they should keep on rolling.

“I would try one of them if I need to get to a meeting downtown, it's a lot faster than going in a car,” Black said.

Both companies plan to expand beyond 500 bikes. Spin says its goal is to have 10,000 bikes throughout Seattle neighborhoods.