Automatic street widening: Evidence from a highway dedication law

Michael Manville


Cities often require developers to widen streets or make other transportation improvements to account for the traffic impacts of new building. This article examines one parcel-level traffic mitigation law in depth—the highway dedication ordinance of the city of Los Angeles. I first show that the law emerged from a combination of happenstance and political and fiscal constraints, not from persuasive evidence it would be effective. I then show that the traffic predictions underlying the law are often inaccurate, and that, in fact, the standards the law is based on are in some ways unverifiable. Thus the law likely does little to reduce congestion and probably impedes housing development. Finally, I argue that the law persists precisely because its desired outcome is hard to verify: Without measurable goals, planners fall back on a measurable process. Parcel-level traffic mitigation becomes an exercise not in reducing traffic but in ensuring that developers carry out mitigations, regardless of whether those mitigations are effective.


transport, land use, street widening, congestion, bureacracy

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Baye, Rachel. 2012. The Price of a Utility Pole: $200,000. Washington Examiner. April 4.

Ben-Joseph, Eran.. 1995. Residential Street Standards and Neighborhood Traffic Control. Berkeley: University of California at Berkeley, Institute of Urban and Regional Development.

Bottles, Scott. 1991. Los Angeles and the Automobile. Los Angeles: UC Press.

Brown, Jeffrey. 2005. A Tale of Two Visions. Journal of Urban History. 4:3-32.

California Supreme Court. 1949. Ayres v City Council. 34 Cal 2d 31. June 14.

City of Los Angeles Department of Transportation. 2010. Traffic Safety Policies and Procedures. July.

Craig Lawson and Co. 2006. Attachment A: Request for Discretionary Approvals and Findings. March 28. Vesting Tentative Tract - 6628B. EAF-2005-8703-EIR.

Duranton, Gilles and Matthew Turner. 2011. The Fundamental Law of Road Congestion. American Economic Review. 101(6):2616-52

Downs, Anthony. 2004. Still Stuck in Traffic. Washington, DC: Brookings.

Estolano, Cecilia. 2006.Adoption of Finding for Benefit Resolution and Authorization to Transfer $605,033 from LA CRA to City of Los Angeles Public Works Trust Fund. LA CRA File 50111, Council File 05-1514 06-0547.

Fehr and Peers. 2010. LA Street Classification and Benchmarking System. Submitted to LA Department of Transportation. October.

Fogelson, Robert. 2004.Downtown. MIT Press.

Glaeser, Edward, 2004. Housing Supply. NBER Research Reporter.

Hahn, Janice. 2005. Motion to Waive Street Widening Requirements at 631-637 South Grand Avenue. CF-2591. November 23.

Handy, Susan. 2013. Smart Growth Trip Generation. Davis: Urban Land Use and Transportation Center of the Institute of Transportation Studies.

Heeb, William. 1961. Staff Report on Proposed Ordinance. Los Angeles City Planning Department. June 29.

Home, Thomas. 1969. Zoning Setback Lines: A Reappraisal. William and Mary Law Review. 10(3):739-754.

Jakle, John and Keith Sculle. 2004. Lots of Parking. Charlottesville: University of Virginia Press.

Los Angeles City Council. Amending Ordinance Nos. 164,305 and 167,137, the Westwood Village Specific Plan. Ordinance Number 176177. Council File 04-019. September 3.

_________. Street width and Sidewalk Standards/Central City area. Council File Number 05-1514). October 15.

Los Angeles Times, 1923. Pasadena Given Clear Roadway. August 1. A7.

McShane, Clay. 1994. Down the Asphalt Path. New York: Columbia University Press.

Merton, Robert. 1957. Social Theory and Social Structure.Glencoe, IL: Free Press, 1957.

Millard-Ball, Adam. 2015. Phantom Trips: Overestimating the Impact of New Development. Journal of Transportation and Land Use. 8(1).

Monlux, John. 1957. Letter to City Council of Los Angeles. Council File 82-318.

Newstrum, Roger 1961. Planning Analyst Report on Proposed Street Dedication Ordinance. September 28. W.A. 18-18.

No Author. 1924. Traffic and City Streets. Public Works.

Norton, Peter. 2008. Fighting Traffic. Cambridge: MIT Press.

Ostrom, Elinor. 1990. Governing the Commons. Cambridge Univesity.

Perry, Jan. 2007. Motion to Waive the 20-foot Street Dedcaitions on Slauson Avenue Between Avalon Boulevard and Central Avenue. Council File 07-2138. July 25.

Proceedings. 1923.Proceedings of the National Conference on City Planning. Available:

Roberts, John. 1961. Letter from Director of City Planning to Mayor Sam Yorty, Council File 82398, 03062, 93665. July 6.

Shoup, Donald. 2003. Truth in Transportation Planning. Journal of Transportation and Statistics.

Swift, P., Painter, D., & Goldstein, M. 1997. Residential Street Typology and Injury Accident Frequency. Congress for the New Urbanism,. Denver.

Schneider, Robert, Susan Handy, and Kevin Shafizadeh. 2015. Method to Adjust Institute of Transportation Engineers Vehicle Trip Generation Estimates in Smart Growth Areas. Journal of Transportation and Land Use. 8(1).

Scott, Anna. 2009. Walkable By Design. Los Angeles Downtown News. January 9.

Spayde, FO. 1925. Eighty Million for City Streets. Los Angeles Times. January 1. 24.

Wachs, Martin. 1990. Regulating Traffic by Controlling Land Use. Transportation. 16: 241-256.

Williams, Leslie. 1923. Traffic in Los Angeles. Los Angeles Times. November 25: 7.

Williams, J. 2008. Along the Wilshire Corridor, CurbedLA. August 11.

The Eastsider. 2011. Street Widening Threatens Silver Lake Palm Trees.