A mobility fee is a one-time charge a local government collects from new development to pay for transportation improvements across the whole network: roads, transit, bike lanes, sidewalks, and trails. Understanding how mobility fees work comes down to four things: what the money can be spent on, how your fee is calculated, when it’s due, and the credits, exemptions, and refunds that can lower what you actually pay.
What a Mobility Fee Pays For
Mobility fees fund the movement of people, not just vehicles. That makes the eligible project list broader than what an older road impact fee covers. Collected revenue can go toward:
- Adding travel lanes, building connector roads, and improving intersection geometry
- Transit capital projects such as dedicated bus lanes, transit stations, and rail infrastructure
- Protected bike lanes, sidewalks, multi-use trails, and pedestrian bridges
- Traffic signals, pedestrian crossings, and intersection lighting
- Adaptive signal control and transit signal priority systems that increase roadway throughput without new pavement
What the fee cannot fund matters just as much. General maintenance, repaving, routine landscaping, and operational costs like bus driver salaries are off limits. The money has to go toward capacity expansion that serves the growth new development creates, not toward fixing existing deficiencies.1Federal Highway Administration. Rational Nexus and But-For Study State of the Practice Report
This also distinguishes a mobility fee from a traditional road impact fee, which funnels money almost exclusively into adding vehicle capacity. If a project sits near transit, a mobility fee can reflect shorter and fewer car trips from that location. Road impact fees rarely make that adjustment.
How Your Fee Is Calculated
Three inputs drive the number: trip generation rate, trip length, and cost per mile. Multiply them together and you have the fee.
Trip Generation
The project gets classified under a standardized land use code from the Institute of Transportation Engineers’ Trip Generation Manual, now in its 12th edition. The manual draws on over 550 study sites spanning single-family homes, shopping centers, warehouses, fitness studios, and more, and assigns each land use type a trip generation rate based on observed behavior.2Institute of Transportation Engineers. Trip Generation: Information
A 100-unit apartment complex and a 2,000-square-foot restaurant generate very different trip patterns, and the ITE codes capture that. If your project doesn’t fit cleanly into an existing code, most jurisdictions let you submit an independent traffic study instead.
Trip Length and Fee Zones
Raw trip counts tell only part of the story. A convenience store generates many short trips. A regional distribution center generates fewer, much longer trips. Mobility fee frameworks multiply the trip count by average trip length, measured in vehicle miles traveled or person miles traveled depending on the jurisdiction.
Most communities carve their territory into mobility fee zones that reflect different densities and travel patterns. A project in a compact urban core carries a shorter average trip length than one on the suburban fringe, which pulls the fee down. The same single-family home can produce a different fee in a downtown infill location than in a suburban zone, even with an identical land use code.
The Formula
Trip generation rate, times average trip length for the zone, times cost per mile set by the jurisdiction’s capital improvement plan. The result scales with both the intensity of the development and its geographic context.
When the Fee Is Due
Payment typically attaches at one of two milestones: building permit issuance or certificate of occupancy. Most jurisdictions require payment at the building permit stage so funds are in hand before the project’s transportation impact begins. Some let you pay as late as the certificate of occupancy.
The process is straightforward. You submit a mobility fee application identifying the land use type, project size, and fee zone. The planning or building department calculates the fee, you pay, and the department issues a receipt or certificate of fee satisfaction that becomes part of the permanent permit file. Without it, the project can’t reach occupancy.
If you think the standard schedule overstates your project’s impact, most jurisdictions let you request an independent fee calculation study. If the study shows lower trip generation or shorter trip lengths than the standard assumes, the fee can be adjusted downward. This is worth pursuing for unusual land uses or for projects with transit access the standard zones don’t fully capture.
Credits for Infrastructure You Build
If you build transportation infrastructure directly instead of just paying the fee, most jurisdictions offer a credit against the mobility fee owed. The credit equals the value of the infrastructure you construct, up to the fee amount.
Typical examples: a road connecting a new subdivision to the existing network, sidewalks and bike lanes required by the site plan, or land dedicated for a future transit corridor. The infrastructure has to be in the jurisdiction’s capital improvement plan. If you build something that wasn’t in the plan, the jurisdiction usually has to amend the plan before it can issue a credit.
Excess credits are trickier. If you build infrastructure worth more than the fee you owe, some jurisdictions let the excess transfer to other projects in the same service area or allow reimbursement from fees collected from future development. Others cap the credit at the fee amount with no reimbursement for the overage. Negotiate these terms before breaking ground, not after.
Exemptions and Reduced Rates
Local rules vary, but common categories for exemption or reduction include affordable housing, government buildings, houses of worship, and projects inside designated redevelopment zones. Review the local fee schedule and ordinance before assuming the standard rate applies to you.
Refunds for Fees That Sit Unspent
A mobility fee has to be spent on its intended purpose within a reasonable timeframe. If the jurisdiction collects your fee but never builds the planned infrastructure, you’re entitled to a refund.
Most jurisdictions set refund deadlines between five and ten years. If the capital improvement funded by the fees isn’t under construction or completed within that window, the original fee payer, or the current property owner depending on local rules, can claim a refund with interest. The government generally has an obligation to identify eligible recipients and process refunds proactively rather than wait for claims.
In practice, few developers track refund eligibility, and unclaimed money is more common than it should be. If you paid mobility fees several years ago and the project those fees were earmarked for hasn’t advanced, checking your refund rights is worth the effort.
When a Mobility Fee Can Be Challenged
Three U.S. Supreme Court decisions set the constitutional outer limits. Under Nollan v. California Coastal Commission, any condition on a development permit has to serve the same purpose that denying the permit would have served, called the essential nexus.3Justia. Nollan v. California Coastal Commission, 483 U.S. 825 (1987) Under Dolan v. City of Tigard, the fee or dedication has to be roughly proportional to the development’s actual impact, based on an individualized determination rather than a generalized assertion that growth causes traffic.4Justia. Dolan v. City of Tigard, 512 U.S. 374 (1994) And under Koontz v. St. Johns River Water Management District, those two tests apply to monetary charges just as they apply to demands for land.5Legal Information Institute (Cornell Law School). Koontz v. St. Johns River Water Management District
The practical takeaway: a jurisdiction that charges every project an identical flat rate without any individualized analysis is exposed. One that ties the fee to project-specific trip generation data and location-adjusted trip lengths is on solid ground. If your fee was calculated using the ITE manual, zone-specific trip lengths, and a published cost per mile, challenging the amount is uphill. If it wasn’t, the nexus and proportionality arguments are the ones to look at.1Federal Highway Administration. Rational Nexus and But-For Study State of the Practice Report