This brief post from KALW looks at the research.
"When calculating travel times, planners don't just calculate how long it actually takes to get from point A to point B. They calculate how long people think it takes. And people think it takes more than twice as long as it actually does.
A recent study by researchers in the Netherlands put a number on it: when asked about how they get around, people perceived transit to take 2.3 times as long as driving a car. Interestingly, that number fell when the people surveyed habitually took transit in addition to driving - they were more familiar with what was involved and planned accordingly."