A family-sized sedan cruises -- or creeps, depending on the day -- along one of the Chicago area's interstates. The car holds only a driver and probably seats full of briefcases, clothing and other clutter.

Sound familiar? It's probably because solo drivers like that one aren't really alone -- they're part of the majority of people who drive to work alone.

According to the Census Bureau, in 2003 almost 80 percent of people commuted to work alone. In 2000, 73 percent of drivers in Illinois drove alone.

Although the costs of driving are increasing -- the average household spent $7,681 on transportation in 2003, according to the Department of Labor -- it is apparently not enough of a deterrent to curb solo drivers.

In the Regional Transportation Authority's new study, driving alone is singled out as the biggest transportation change in Chicago from 1990 to 2000. The increase in driving alone took riders away from bus and carpool travel, the report stated.

Putting more cars on the road could mean more congestion, longer commute times and more pollution. But going it alone may be the best, or only, option for most Chicago-area residents.

Siim Soot, a professor at the University of Illinois-Chicago, and the former director of the school's Urban Transportation Center, said public transportation works best where there is dense development. But jobs aren't located in those areas.

And as much as Metra and Pace may try to expand services to meet the job demand, they will probably never be able to cover all the scattered job areas.

"(Chicago has) grown so substantially, jobs are so dispersed, and it's difficult for two people to go out of their way to reach job locations," he said.

The RTA's Moving Beyond Congestion report said 30 percent of Chicago workers in 2000 traveled outside the city to work. And, of the 257,000 commuters added in the 90s, two-thirds worked in collar counties.

But the new job destinations don't look like the old ones downtown. Employees can't walk around the corner to grab a bite to eat, and running errands almost certainly requires a car. Plus, a competitive nature often leads employees to go it alone.

"We're becoming more competitive in many ways -- working later hours, unusual hours," Soot said. "Even if (commuters) lived and worked close to each other, it's unlikely they'd have the same work hours. The overall flexibility that people need overrides other considerations."

The cost of driving alone

Several organizations have calculators that will determine the cost of driving alone for a particular type of car.

The calculations usually take into account gas, maintenance, insurance, depreciation and parking.

The Chicago Area Transportation Authority has a calculator available atwww.catsmpo.com/ride-commuting-costs.htm. On that calculator, an 80-mile round trip in a mid-sized vehicle would cost $6,768 per year.

The Seattle Monorail Project has a more detailed calculator that allows specific information on insurance cost and vehicle depreciation to be entered.

It can be found at www.elevated.org/project/funding/driving/