Out of town bypasses

Out of town bypasses are roads that avoid built-up areas such as towns, cities, or commercial/business districts. Typically designed for higher speed limits, bypasses are intended to allow travelers, including trucks, to continue at highway speeds and reduce through traffic congestion within towns and cities. Bypasses may incorporate more than one town, looping around rural communities (Cena 2011).

Expected Beneficial Outcomes (Rated)

  • Reduced injuries

  • Increased pedestrian and cyclist safety

Other Potential Beneficial Outcomes

  • Improved quality of life

  • Improved sense of community

  • Reduced emissions

Evidence of Effectiveness

There is some evidence that out of town bypasses decrease traffic injuries and increase pedestrian and cyclist safety (Egan 2003*, Cena 2011, Elvik 2001*, Thomson 2008). Additional evidence is needed to confirm effects.

Out of town bypasses have been shown to decrease traffic injuries on both main roads through town and on bypass roads (Cena 2011, Elvik 2001*, Thomson 2008). Out of town bypasses appear to reduce truck traffic on main roads through town (Mills 2011*, Orr 2012*). A New Zealand-based study suggests out of town bypasses may also increase cycling and cyclist safety when cycleways or bike paths are included (Orr 2012*). Bypasses can reduce social disturbances such as noise levels (Gaffney 2017, Ramis 2003*), support community cohesion, and improve overall quality of life in towns (Ramis 2003*), and reduce particulate matter pollutants near the bypassed road (Burr 2004).

Bypasses are often located in less populated areas, since changing traffic flow may increase air pollution (Thomson 2008) and noise levels, and decrease community cohesion near the bypass (Egan 2003*, Thomson 2008). In some instances, out of town bypasses may shift crash locations, modestly reducing effects on overall crash rates (Elias 2011*).

Experts suggest that bypass routes can be effectively incorporated into previously established networks by transit planners (Gaffney 2017).

Impact on Disparities

No impact on disparities likely

Implementation Examples

Bypass roads are found in urban, rural, and suburban areas throughout the US, although design and operational practices vary (US DOT-FHWA).

Implementation Resources

CUTR-Bypass - Center for Urban Transportation Research (CUTR). What to expect when you’re expecting a bypass: Webinar and bypass basics brochure. Tampa, FL: Center for Urban Transportation Research (CUTR), University of South Florida (USF); 2014.

Citations - Evidence

* Journal subscription may be required for access.

Egan 2003* - Egan M, Petticrew M, Ogilvie D, Hamilton V. New roads and human health: A systematic review. American Journal of Public Health. 2003;93(9):1463-71.

Cena 2011 - Cena LG, Keren N, Li W, et al. A Bayesian assessment of the effect of highway bypasses in Iowa on crashes and crash rate. Journal of Safety Research. 2011;42(4):241–52.

Elvik 2001* - Elvik R, Amundsen FH, Hofset F. Road safety effects of bypasses. Transportation Research Record: Journal of the Transportation Research Board. 2001;1758(01):13–20.

Thomson 2008 - Thomson H, Jepson R, Hurley F, Douglas M. Assessing the unintended health impacts of road transport policies and interventions: Translating research evidence for use in policy and practice. BMC Public Health. 2008;8:339.

Mills 2011* - Mills J, Fricker J. Integrated analysis of economic impacts of bypasses on communities: Panel data analysis and case study interviews. Transportation Research Record: Journal of the Transportation Research Board. 2011;2242:114-121.

Orr 2012* - Orr J. The Ruby Bay bypass – The project that pushed the boundaries. Proceedings of the Institution of Civil Engineers - Municipal Engineer. 2012;165(4):215-218.

Gaffney 2017 - Gaffney JL, Bunker JM, Dawes LA. An investigation into the need for highway bypass development. Australasian Transport Research Forum; 2017.

Ramis 2003* - Ramis J, Alba J, Garcia D, Herna F. Noise effects of reducing traffic flow through a Spanish city. Applied Acoustics. 2003;64(3):343-64.

Burr 2004 - Burr ML, Karani G, Davies B, Holmes BA, Williams KL. Effects on respiratory health of a reduction in air pollution from vehicle exhaust emissions. Occupational & Environmental Medicine. 2004;61(3):212-8.

Elias 2011* - Elias W, Shiftan Y. The safety impact of land use changes resulting from bypass road constructions. Journal of Transport Geography. 2011;19(6):1120–9.

Citations - Implementation Examples

* Journal subscription may be required for access.

US DOT-FHWA - US Department of Transportation (US DOT). Federal Highway Administration (FHWA).

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