The third annual Drive Less Challenge kicked off April 22, and so far 400 people have signed up, according to founder Adina Levin.

The event started in Menlo Park in 2009 with 120 participants. The goal is to do exactly what the name of the event implies - find ways to spend less time traveling by car without sacrificing your lifestyle.

Ms. Levin, who serves on the city's Environmental Quality Commission, said Menlo Park's weather and flat terrain, as well as access to Caltrain and the variety of services available downtown, help make the challenge viable.

Other local features make it tougher, she said. "There are some challenges with transit access. Caltrain's schedule is less convenient in midday and evening."

"And there are challenges in car-oriented habits and mindset," she said. "For example, there is sometimes a big traffic jam at the Alma Street parking lot by the library and gym, and city commissions proposed a variety of improvements -- but not walking and biking to the gym and library."

Participant Kathy Schrenk said her biggest frustration is leaving Menlo Park to head north to Redwood City without a car. "I live right by El Camino, but the bus schedule is rarely convenient," she said. "There's also no way to easily bike there; your choices are scary -- El Camino or Middlefield."

She's also found it hard to travel by bike from Atherton, thanks to a wall along Bay Road. Weekly trips have shown her that residents in that area would either have to take a "terrifying" ride down Marsh Road or travel all the way to Ringwood Avenue."It's a big inconvenience," Ms. Schrenk said.

Those points aside, she said she finds getting around Menlo Park without a car very convenient between Middlefield Road and Alameda de Las Pulgas, thanks to the concentration of schools and services.

The Drive Less Challenge runs through May 5. Local merchants give prizes to top performers in participating cities, which this year includes Menlo Park, Palo Alto, Mountain View, East Palo Alto, Los Altos, Los Altos Hills, Foster City, Burlingame, San Carlos, and Sunnyvale.

According to event staff, 900 participants replaced some 9,000 solo car miles with alternative "green" trips last year, reducing local CO2 emissions by nearly 45,000 pounds.

Go to the event website to sign up or share tips. Event staff reported that more than half of participants continue the new travel practices they tried during the two-week challenge.