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Center for Advancing Research in Transportation Emissions, Energy, and Health (CARTEEH)

A USDOT University Transportation Center

Alteration of the Roadway Alignment

Shifting the roadway, either horizontally or vertically, is one noise abatement measure considered by some state DOTs.1 Horizontal alignment alterations is when roadways are shifted further away from noise-sensitive receptors, while vertical shifts involve either raising or lowering the roadway. This strategy may be combined with green infrastructure solutions, such as positioning the roadway between hills or wooded areas.2

Considering this strategy will help achieve the goal of the following objectives

  • Less Contamination
  • Less Emissions
  • Less Traffic Noise
  • Connectivity and Inclusion
  • Healthy Destinations
  • Less Traffic Violence
  • Active Transportation
  • Green Space

Transportation lifecycle phases

This strategy is associated with the following transportation lifecycle phases:

  • Construction
  • End of Life
  • Maintenance
  • Material Selection
  • Operations
  • Policy and Planning
  • Project Development

Who's involved

  • Construction companies
  • Local governments
  • Policymakers
  • Transit agencies
Shifting the roadway, either horizontally or vertically, is one noise abatement measure considered by some state departments of transportation (DOTs).1 Horizontal alignment alterations is when roadways are shifted further away from noise-sensitive receptors, while vertical shifts involve either raising or lowering the roadway. This strategy may be combined with green infrastructure solutions, such as positioning the roadway between hills or wooded areas.2

How it Helps

By increasing the separation between the source and receiver, horizontal alignment shifts can decrease noise exposure to the surrounding communities. Vertical alignment shifts can operate similar to noise barriers by disrupting the distribution of traffic noise.

Implementing

Design Process:
Typically, alterations in roadway alignment occur very early on in the transportation design process and it limited to new roadways or major reconstruction activities.2,3 It will also depend on space constraints, existing roadways, and other factors. For example, horizontal alignment shifts are typically only appropriate if there is vacant land surrounding the roadway.
Cost Considerations:
The construction costs of altering a roadway’s alignment can vary between horizontal and vertical shifts. Whereas horizontal alignment shifts are usually very expensive, vertical alignment shifts may be less expensive if the right-of-way is sufficient.1

Examples

1) Texas A&M Transportation Institute (TTI) Report on Roadway Designs
TTI, in conjunction with TxDOT and USDOT, conducted a four-year study to evaluate the social, economic, and environmental impacts of elevated or depressed roadway designs. The study concluded that depressed freeways provide significant reductions in traffic noise, especially if additional noise abatement measures (such as solid guardrails or low-noise pavements) are implemented.
1. Rochat, J., et al. (2020). Summary of Noise-Reducing Strategies. National Cooperative Highway Research Program. https://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP25-57TechMemo.pdf
2. AASHTO Center for Environmental Excellence. Traffic Noise & Transportation. https://environment.transportation.org/education/environmental-topics/traffic-noise/traffic-noise-overview/
3. New Hampshire Department of Transportation. Noise Barrier Programs. http://www.everettturnpikewidening.com/documents/NHDOT%20Noise%20Barrier%20Programs.pdf