🛑 Facing a Problem with High Trip Generation?
You’ve run your numbers.
The Trip Generation Estimate is way above what the local road network can handle.
Your Traffic Impact Study (TIS) or Traffic Impact Assessment (TIA) shows intersections failing, and the city wants costly mitigation.
Now what?
This is where Travel Demand Management (TDM) can help. You can use some of these strategies in your TIA report. If you currently making a report, try creating one using this free template.
🚦 What Is Travel Demand Management?
Travel Demand Management (TDM) refers to a set of policies and strategies designed to reduce the number of single-occupancy vehicle (SOV) trips generated by a development, especially during peak periods.
The goal is not just to shift trips to off-peak times — but also to replace car trips with transit, walking, cycling, or ridesharing, and eliminate unnecessary travel altogether.
🎯 Why Use TDM in Development Projects?
TDM strategies are often used when:
- A development’s trip generation exceeds local thresholds
- Road improvements are financially or physically unfeasible
- A city requires TDM mitigation to approve your rezoning or site plan
Many jurisdictions allow trip credit reductions for approved TDM plans — often ranging from 5% to 30%+ depending on the strategy and context.
✅ Top 10 TDM Strategies (with Typical % Trip Reduction)
Here are 10 effective, research-backed TDM measures and their typical trip reduction percentages, based on sources like ITE, NCHRP Report 708, FHWA, and local TDM guidelines (e.g., San Diego, Ontario, Seattle, Portland):
1. Transit Subsidies or Free Transit Passes
- What: Offer free or discounted monthly passes to tenants or employees
- Who it works for: Office buildings, apartments, large employers
- Typical Trip Reduction: 5–15%
2. Unbundled Parking
- What: Separate parking costs from rent/sale price so residents pay only if they need parking
- Who it works for: Residential or mixed-use developments
- Typical Trip Reduction: 10–20%
3. Carpooling Programs & Preferred Parking
- What: Reserved spots for carpoolers + internal ride-matching platform or app
- Who it works for: Employers, schools, office parks
- Typical Trip Reduction: 5–10%
4. Bicycle Facilities & Amenities
- What: Provide secure indoor bike parking, repair stations, and showers
- Who it works for: Offices, universities, residential towers
- Typical Trip Reduction: 2–5%, but up to 10% near good cycling networks
5. Onsite Carshare Vehicles (e.g., Zipcar, Communauto)
- What: Provide dedicated carshare vehicles on site with promotions for residents or employees
- Who it works for: Residential and commercial sites in urban areas
- Typical Trip Reduction: 5–12%
6. Employer-Based TDM Coordinator & Programs
- What: Hire a dedicated TDM manager to promote commuting alternatives and run incentives
- Who it works for: Corporate campuses, institutions
- Typical Trip Reduction: 5–10%, higher if paired with incentives
7. Active Transportation Connectivity Improvements
- What: Build or enhance walking and cycling paths connecting the site to nearby networks
- Who it works for: All types of development
- Typical Trip Reduction: 2–8%
8. Shuttle Service to Transit Hubs
- What: Private shuttle from the development to nearby train or BRT stations
- Who it works for: Suburban campuses, residential towers, hospitals
- Typical Trip Reduction: 8–15%
9. Flexible Work Hours / Telework Policies
- What: Encourage or mandate staggered shifts and remote work options
- Who it works for: Office and institutional developments
- Typical Peak Trip Reduction: 5–15%
10. Mobility-as-a-Service (MaaS) Platform Integration
- What: Provide digital access to trip planning and payment for multiple modes (transit, bike, carshare)
- Who it works for: Urban mixed-use projects
- Typical Trip Reduction: 2–5%, higher with incentives
📊 Sample Trip Reduction Scenario
Let’s say your residential tower generates:
- Peak Hour Trips (Unmitigated): 220
With a combined TDM strategy:
- Transit pass subsidy: –10%
- Unbundled parking: –12%
- Bike amenities: –3%
Adjusted Peak Hour Trips = 220 × (1 – 0.10 – 0.12 – 0.03) = ~168 trips
You’ve cut 52 trips (24%) — enough to drop one critical intersection from LOS F to LOS D.
That’s the power of proactive TDM.
🧠 Key Tips for Planners and Engineers
- Always use conservative trip reduction assumptions unless supported by local policy
- Reference TDM manuals or approved mitigation rate sheets from the local jurisdiction
- Monitor and report: Some cities require a TDM Monitoring Plan or performance tracking post-occupancy
- Ensure site design supports non-car travel: entrances near transit, bike access, wayfinding
🛠️ Use Arterials.co Tools to Strengthen Your Case
Need to estimate trips before and after mitigation? Try:
- 📈 Trip Generation Estimator Tool
- 🅿️ Parking Demand Estimator
- ⚠️ Signal Warrant Calculator (to check if your mitigated volumes still trigger a signal)
These tools can help refine your TIS/TIA and build a stronger case for approval with fewer physical upgrades.
🏁 Final Thoughts
Traffic Impact Assessments don’t always require expensive infrastructure changes.
With the right TDM strategies, you can reduce car trips, lower your peak-hour impact, and get your project approved faster — all while promoting sustainable transportation.
💡 Next time your trip numbers come in too high, try managing demand instead of just expanding supply.
