By Mike Spack, PE, PTOE
My apprentices (Mike Bultman, Joe Collins, Kirk Pettis, and Jenni Thompson) put in a lot of hard work collecting and analyzing traffic generation and parking generation data from six office complexes in Minnesota who are actively implementing Travel Demand Management (jargon alert: TDM) strategies. Here is the full, twelve page report – Download Travel Demand Management Effectiveness Report. It doesn’t include all of our underlying data, but we’re happy to share that if there’s a researcher out there who wants to slice and dice in a different way.
Overall, TDM plans do appear to have a positive effect on traffic generation and parking numbers in buildings with TDM plans in place when compared to the Institute of Transportation Engineers published standards. Based on the analysis performed for this study, on average, TDM plans reduce traffic generation rates by 27% to 37% and parking generation from 11% to 21% depending on the time of day and other variables.
If office buildings implement a thorough TDM plan, they will generate less peak hour traffic and require fewer parking stalls. We recommend practitioners use a 30%
reduction in traffic generation (compared with the Institute of Transportation Engineers’ standard rates) when assessing the traffic impacts of a proposed office building that will implement a TDM plan. We recommend practitioners use a 10% reduction in parking stall requirements (compared with the Institute of Transportation Engineers’ standard rates) for office building that will implement a TDM plan.
These are significant findings.
The reduction in traffic generation could often be the difference between needing to install a traffic signal or not, typically a $200,000 expenditure. In Minnesota, a surface parking stall costs between $3,000 and $4,000 to build while a stall in a parking ramp costs between $15,000 and $20,000. This means the 181,000 square foot office labeled Site B could have built 245 parking stalls instead of 270 stalls, saving $75,000 to $100,000 in construction costs. This does not factor in lower maintenance costs, lower environmental impacts, or the higher employee satisfaction benefits Travel Demand Management provides.