They drive alone and show up in droves -- that much is clear.

But who are these non-carpooling commuters? Where do they come from? And, most importantly, what can the city do to get them to switch from cars to other forms of transportation?

These questions have for years mystified the City Council, which has spent more time discussing parking and traffic than just about any other topic over the past two years. And now, at last, the city has some answers.

The Palo Alto Transportation Management Association (TMA), the city's recently formed traffic-fighting nonprofit, commissioned a detailed survey of downtown commuters. The consulting firm EMC surveyed 1,173 people in the downtown area, including employees of small-, medium- and large-sized companies. Each was asked a list of questions about city of origin, commute patterns and attitudes about biking, transit and other transportation options.

The survey, which was conducted in May, revealed that about 55 percent of people drive by themselves into downtown Palo Alto. The largest share of commuters, 33 percent, come here from the South Bay. They were followed by drivers from the Peninsula (20 percent) and from other parts of Palo Alto (also 20 percent). A minority came from San Francisco (10 percent) and the East Bay (7 percent).

One of the survey's most striking findings is South Bay and East Bay commuters are far more likely to drive alone to Palo Alto than their counterparts from San Francisco. Only 18 percent of commuters from San Francisco drive alone, according to the survey. This is compared to 76 percent of commuters from East Bay, 65 percent of commuters from South Bay and 63 percent of commuters from the Peninsula. Of those who live in Palo Alto, 41 percent drive alone to work while 48 percent either walk or bike.

The survey also showed that part-time workers are far more likely to drive alone than full-timers and that employees of large businesses are less likely to drive alone than employees of medium-sized businesses and small ones. Of the workers with one full-time job, 53 percent drive alone, while those with one part-time job have a rate of 75 percent.

The survey also indicated that coders are much less likely to drive than chefs, hotel workers, shopkeepers or just about any other type of downtown employees. And the gap is wide, with tech workers making up 39 percent of survey respondents (hospitality was a distant second with 16 percent).

Yet only 33 percent of tech workers indicated that they drive alone, while 31 percent take Caltrain and 26 percent walk or bike. The drive-alone rate for those in retail is 78 percent; in hospitality it's 73 percent; and in the restaurant sector it's 72 percent.

The survey's conclusion about tech workers eschewing their cars is largely consistent with the data collected earlier this year by downtown tech companies Palantir, SurveyMonkey and RealIQ. The three companies surveyed their employees and determined that only 38 percent drive alone.

"Mode share is obviously highly dependent on where the respondent is traveling from," the survey from the three firms concluded. "Individual car share is very high in places with poor Caltrain access. Proximity to work (which allows for walking and biking) and access to Caltrain are two major factors in determining mode share."

When it comes to Caltrain, San Francisco's commuters are far ahead of the pack. The survey showed 70 percent of them rely on Caltrain to get to work, compared to just 20 percent of South Bay residents and 16 percent of those who come from other Peninsula cities.

In general, those with the most distance to cover were shown to be more likely to depend on transit. Of the commuters with trips longer than 50 miles, 38 percent reported driving alone while 40 percent rely on Caltrain. Those with shorter trips, between 10 and 50 miles, generally favor cars over trains and buses. The survey showed that 69 percent of them drive alone, while 19 percent take Caltrain.

The survey results are already influencing Palo Alto's debate about traffic and parking. On Monday night, the council had a long discussion about transportation projects that they'd like to see funded in the coming years.

The study's findings about the high number of people who commute from South Bay to Palo Alto were cited by council members who argued that the city should demand more money for transit services from the Santa Clara Valley Transportation Authority (VTA), which is now moving ahead with a plan to put a transportation measure on the November 2016 ballot.

The new data is also expected to affect the wave of parking and transportation initiatives that the city is preparing to launch. These include the parking-permit program in downtown's residential neighborhoods, valet programs in downtown garages, Caltrain passes for City Hall employees, and the expansion of the city's small shuttle system.

Jessica Sullivan, the city's transportation planning manager, called the survey "pretty significant" in giving the city insight into the travel habits of downtown employees. Results will be used by the city to consider the best strategies to use in supporting employees going downtown. They data will come in particularly handy in the next few months, as the TMA begins unveiling pilot programs aimed at getting drivers out of cars (incidentally, 49 percent of those who drive alone appear be open to this idea, according to the survey).

Sullivan said the city is also launching an effort to develop a five-year plan for the shuttle system. The study will take a look at who the shuttles are serving and what the coverage gaps are.

"Our idea is to make the shuttle a really important part of the mobile services here in Palo Alto," Sullivan said.

The new data won plaudits from the council, with Tom DuBois saying it "gives us a good blueprint" for action. He noted that the survey shows, among other things, that tech workers aren't the problem when it comes to commuting behavior.

"We need to apply this data and have a more sophisticated discussion about parking," he said.

Councilman Marc Berman also said he was fascinated by finding that only a third of downtown's tech workers drive alone. Their mode share (31 percent took Caltrain and 21 percent walked or biked) exceeded his expectations, Berman said.

"But restaurants, retail and hospitality -- those are areas where we can really make a lot of gains," Berman said.

The council's discussion came just weeks before the expected launch of downtown's long-awaited Residential Preferential Program, which will institute a time limit for parking in residential neighborhoods for cars without a permit. The city began selling permits over the weekend and as of Monday afternoon, had sold about 400 on its website. Enforcement of the program will begin on Sept. 15 and planning officials will spend six months monitoring the program and gathering data before revising the program based on the data collected.

Though it remains to be seen whether the program will succeed in relieving downtown's parking problem, council members were ecstatic on Monday about just getting to the starting line. Berman noted during the discussion that the council's work to date consisted of approving policies and going through planning phases.

"Now is the most exciting time," Berman said. "It's execution time."