While this is technically a table and not a chart, it’s still interesting. It’s a table from a study about what kind of influence parking benefits (e.g. free parking for employees) has on people’s tendency to drive vs. take transit vs. bike to work.
The idea here is that if you provide free parking for your employees, they’ll be more likely to drive and less likely to take any other mode of transportation. Here’s the conclusion from the study:
Overall, our results support earlier findings in the literature that suggest com- muter benefits for walking, cycling, and public transportation may be effective at supporting TDM objectives. Free car parking tends to be associated with more driving to work, public transportation benefits tend to be associated with riding public transportation, and trip-end facilities at work such as showers/lockers and bike parking tend to support walking or cycling. Our results also add to the literature by presenting an evaluation of the joint supply of benefits. While benefits for alternatives to driving are associated with individuals choosing to walk, cycle, and ride public transportation, free car parking is associated with driving, and the joint provision of free car parking along with these other benefits may blunt the efficacy of efforts to get commuters to walk, cycle, and ride public transportation to work.
Check out the whole report here.