Santa Rosa is gearing up to take a couple of parking meters for a test drive this week.

The city is set to roll out two new styles of single-space parking meters in the 600 block of 4th Street downtown to help determine which is the best fit for downtown.

The month-long pilot project, prompted by a petition from downtown merchants critical of the paper-based parking kiosks, is designed to see which units the public prefers and which work best with the city's internal systems.

Two rival parking meter manufacturers — IPS Group of San Diego and Duncan Solutions of Milwaukee — submitted bids to the city that were very similar, prompting the city to stage the parking meter face-off.

"We really thought it was necessary to see the equipment in operation and let the public use it so we can make sure we make the best choice," said Kim Nadeau, the city's parking coordinator.

Twenty meters from each company were installed last week but remain covered with plastic bags until tests can be completed allowing the units to go live, probably on Wednesday, Nadeau said.

Most are installed side-by-side in two-meter housings, allowing their features to be easily compared.

The units are very similar.

Both accept credit and debit cards and coins. Both have digital screens displaying how much time remains. Both are solar powered. And both flash to alert meter readers when the time is expired.

There are differences, though.

The Duncan Solutions meters have a curved top, reminiscent of the classic parking meters and other single-space meters installed in other parts of the downtown.

The IPS meters have a more modern look, sporting a diamond-shaped head.

Another difference is in the system used to detect whether a vehicle is in a parking space.

The Duncan system has a radar-based sensor located on the pole. The IPS system uses a hockey-puck-sized magnetic sensor embedded in the ground.

Both detect when a vehicle is present in the space, information that can be used to wirelessly alert an enforcement officer when the time has elapsed, or to zero-out the meter after a car leaves.

The city is planning to use the sensors to zero-out some of the meters during the pilot project, which will mean no more freebies for people lucky enough to pull into a space with time left on the meter.

But the city is not planning to "push" that data out to enforcement officers just yet, although that is possible in the future, Nadeau said.

Another difference in the new meters is their height. At 48-inches, they are nine inches shorter than other single-space meters in the city. The lower height is to accommodate people with disabilities so they can reach them from a wheelchair, Nadeau said.

Even though many disabled drivers are entitled to free parking under state law, some may not have the required placard, Nadeau said.

Cities like San Francisco and Sacramento are installing the meters at the lower height for the same reason, she said. The city plans to phase in new meters at the lower height in the future, she said.

"It may become more common in the not-too-distant future to see these lower heights for single-space parking meters throughout the state," she said.