Transportation Engineers

by

CARL

Table Of Contents
  1. Overview
  2. Action 1: Embed emissions metrics into project evaluation
  3. Action 2: Advocate for mode-shift infrastructure in your project designs
  4. Action 3: Challenge induced demand assumptions in your traffic models
  5. Bonus: Find allies in other departments and groups
  6. Resources

Overview

Who is this guide for?

If you’re a transportation engineer and you’re asking yourself, “How can I make my job more environmentally friendly when my work involves designing roads, managing traffic systems, and planning infrastructure that will lock in emissions for decades?” … then this Climate Action Guide is for you.

Transportation engineers design and maintain the systems that move people and goods such as roads, transit corridors, intersections, freight networks, and the policies that govern them. Those decisions have outsized climate stakes: transportation is one of the largest sources of greenhouse gas emissions in the United States, accounting for roughly 28% of total emissions. As a transportation engineer, you sit at the controls. Your specifications, your models, and your design choices shape how millions of people travel, and whether those patterns accelerate or slow down climate change. This guide offers three concrete actions you can take within your existing role, starting now.

How can a transportation engineer take climate action

  1. Embed emissions metrics into project evaluation: Make carbon a standard criterion alongside cost and traffic performance
  2. Apply traffic demand management in your models: Design projects that make walking, cycling, and transit genuinely competitive with driving
  3. Apply traffic demand management in your models: Challenge induced demand assumptions and model lower-VMT scenarios as viable alternatives

Taking climate action benefits everyone

  • Transportation engineers and teams: Develop in-demand skills, work on more resilient and future-proof infrastructure, and strengthen project justifications for grant funding
  • Employers: Access federal and state green infrastructure funding, reduce lifecycle costs, and build credibility with climate-conscious clients and municipalities
  • Community and environment:
    • Reduce transportation-sector greenhouse gas emissions
    • Improve air quality and public health outcomes in communities near roadways
    • Build infrastructure that is more resilient to climate-related disruption

Action 1: Embed emissions metrics into project evaluation

Transportation projects are routinely evaluated on traffic level of service (LOS), construction cost, and safety — but lifecycle carbon is rarely a first-class metric. Adding emissions analysis to project scoring changes what gets built and how it gets designed. Vehicle Miles Traveled (VMT) measures the total distance driven by all vehicles in a given area over a given period, and is used as a proxy for transportation-related greenhouse gas emissions and traffic impact. In 2020, California became the first state to replace Level of Service (LOS), which measures traffic delay and congestion, with VMT as the primary metric for evaluating transportation impacts under CEQA, shifting the focus from driver convenience to emissions and land use outcomes. Other states like Oregon, Minnesota and Colorado have also made the switch.

Why it matters

A lane expansion that looks cost-effective on a 20-year traffic model may generate decades of induced vehicle miles traveled (VMT). A pedestrian bridge or protected bike corridor may have a fraction of the embodied carbon and zero operational emissions. When carbon isn’t measured, it can’t be optimized.

Step-by-step

  1. Add a GHG analysis layer to existing project templates: Use tools like FHWA’s MOVES model, Cal-B/C (for California projects), or the Infrastructure Carbon Estimator to estimate operational and embodied emissions for project alternatives. These don’t require new software licenses as they’re publicly available.
  2. Propose a carbon score in your project evaluation matrix: Work with your team to add emissions (tons CO₂e over project lifetime) as a weighted criterion alongside cost-per-mile and LOS. Even a small weighting starts surfacing tradeoffs.
  3. Document the methodology: Write a one-page protocol your team can reuse. Standardization is what turns a one-off analysis into department practice.
  4. Reference funding incentives: Federal programs including the EPA’s Clean School Bus program reward projects with measurable emissions benefits. Carbon metrics in your evaluation documents directly support grant applications.

References

Action 2: Advocate for mode-shift infrastructure in your project designs

Transportation engineers don’t just respond to demand, they shape it. Infrastructure designed around the car produces car-dependent travel patterns. Infrastructure that makes walking, cycling, and transit safe and fast produces different behavior. Advocating for mode-shift within projects you’re already working on is one of the highest-leverage climate actions available to you.

Why it matters

Vehicle miles traveled (VMT) reduction is the most direct path to transportation emissions cuts. Mode shift (moving trips from single-occupancy vehicles to walking, cycling, or transit) is the fastest way to achieve VMT reduction without waiting for fleet electrification to mature. Engineers who embed multimodal infrastructure into project scope expand what’s possible without requiring entirely separate projects.

Step-by-step

  1. Review every project scope for multimodal opportunity: When a road resurfacing or intersection redesign comes across your desk, ask: is there right-of-way available for a protected bike lane, wider sidewalk, or bus queue jump? Resurfacing projects are the lowest-cost opportunity to add multimodal infrastructure.
  2. Use the NACTO Urban Street Design Guide standards: NACTO’s guidelines provide defensible, peer-reviewed design specifications for protected lanes, transit priority signals, and pedestrian realm improvements. Citing established standards makes it easier to advocate for design changes internally.
  3. Model the mode-shift scenario: Run a trip generation comparison that includes induced transit or cycling demand alongside vehicle demand. Present it alongside the conventional scenario. The comparison itself shifts the conversation.
  4. Connect with your municipality’s active transportation or sustainability staff: In most cities, there are planners actively working on safe streets, Vision Zero, or climate action plans who need engineering partners to make designs real. Find them and establish a working relationship.

Related action: Advocate for signal timing that prioritizes transit vehicles and pedestrians during peak hours, a low-cost intervention with measurable mode-shift effects.

References

Action 3: Challenge induced demand assumptions in your traffic models

Traffic models have enormous power over what infrastructure gets built, and conventional four-step travel demand models are structurally biased toward projecting traffic growth that then justifies road expansion. Transportation engineers who understand this can apply more accurate assumptions and advocate for lower-VMT scenarios as credible project alternatives.

Why it matters

Induced demand, the well-documented phenomenon whereby new road capacity generates new vehicle trips, is frequently underestimated or omitted in project models. The result is infrastructure that fails to relieve congestion while locking in decades of emissions. Engineers who surface induced demand in their models, and who model transit investment as a genuine alternative to capacity expansion, produce more accurate analyses and create space for better decisions.

Step-by-step

  1. Apply an induced demand elasticity factor in your VMT projections: Research (including work by UC Davis’s National Center for Sustainable Transportation) consistently finds VMT elasticity with respect to lane miles of approximately 1.0 over the long run: meaning a 10% increase in capacity produces roughly a 10% increase in VMT. Add a sensitivity scenario that includes this factor and present it alongside the base case.
  2. Model the no-build and transit-investment alternatives with equal rigor: Federal NEPA requirements call for alternatives analysis, but transit and no-build alternatives are often modeled with less effort than the preferred build. Apply the same analytical care to all alternatives.
  3. Use the Rapid Assessment of Transportation Climate Impacts (RATCI) tool: Developed for state DOTs and MPOs, RATCI allows you to quickly estimate GHG impacts of different project types. It provides external credibility for emissions scenarios in your models.
  4. Document your assumptions transparently: Write a clear assumptions memo for each model run that includes the induced demand elasticity used, the growth rate source, and the mode split assumptions. Transparent assumptions invite review and improvement, and make it easier to advocate for more accurate inputs over time.

Related action: Attend a Traffic Analysis for a Changing Climate training through American Society of Civil Engineers (ASCE), Institute of Transportation Engineers (ITE) , or your state’s transportation agency. Building technical vocabulary for these conversations makes internal advocacy more effective.

References

Bonus: Find allies in other departments and groups

Transportation engineers never work alone. The climate case for better transportation infrastructure is being made across multiple disciplines; connect with the people already making it.

Potential allies

  • Urban planners and land use staff: Land use and transportation are inseparable. Planners working on mixed-use zoning or transit-oriented development are natural partners.
  • Municipal sustainability and climate offices: Many cities have climate action staff actively looking for engineering partners to move infrastructure projects forward.
  • MPO (Metropolitan Planning Organization) staff: MPOs control regional transportation funding and modeling frameworks. Building relationships there creates leverage on the modeling assumptions that shape project selection across your region.
  • Active transportation advocates and Vision Zero coalitions: Community organizations often have political capital that complements technical credibility.
  • Institute of Transportation Engineers (ITE) Sustainability Committee and the American Society of Civil Engineers (ASCE) Sustainability Committee: Peer networks for engineers integrating climate into practice.

Resources

California Senate Bill 743 (SB 743) — LOS to VMT

Contributors

Jack Lucero Fleck and Mike Sallaberry

It’s your turn: What climate actions have you taken as a Transportation Engineers? What other actions should we list? Please share your experiences with us.