Evaluating Sidewalk Infrastructure & Prioritizing Investment

Coppola, Nick; Marshall, Wesley · 2021 · ROSA P / Washington State University. National Center for Transportation Infrastructure Durability & Life Extension (TriDurLE) UTC

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Summary

This study addresses the critical lack of comprehensive sidewalk data in urban planning, specifically focusing on how static obstructions impact pedestrian accessibility. While cities increasingly prioritize active transportation, existing research often relies on incomplete spatial data that ignores obstacles like utility poles, trees, and street furniture. The authors argue that failing to account for these obstructions leads to a gross overestimation of sidewalk adequacy. The research aims to bridge this gap by leveraging high-resolution remote sensing and planimetric data to calculate accurate "clear width"—the unobstructed space available for pedestrians—at a city scale, and to develop a methodology for prioritizing infrastructure investment. The methodology utilized planimetric data from Cambridge, Massachusetts, selected for its high-quality aerial imagery and comprehensive obstruction datasets. Using Quantum GIS (QGIS), the researchers processed 1,523 sidewalk polygons and over 30,000 static obstructions. They developed a specific algorithm to calculate minimum clear width by generating centerline points at one-foot intervals and measuring distances to sidewalk boundaries and obstruction edges. Obstructions represented as points or lines were converted to polygons using conservative dimension estimates derived from city records and online sources. The study compared clear width measurements with and without obstructions against standards from the Americans with Disabilities Act (ADA), Federal Highway Administration (FHWA), and other agencies. Additionally, the project combined this spatial data with vehicle and pedestrian trip big data to create a prioritization framework for identifying areas needing infrastructure attention. The results demonstrate a significant discrepancy in sidewalk accessibility when static obstructions are considered. On average, sidewalk clear width decreased by 22%, dropping from 4.5 feet to 3.5 feet. More critically, the median clear width fell by nearly 32%, from 4.4 feet to 3.0 feet. This reduction places the median sidewalk exactly at the ADA’s minimum three-foot requirement, implying that approximately half of Cambridge’s sidewalks fail to meet accessibility standards when obstructions are accounted for. In contrast, ignoring obstructions would have suggested that 78% of the sidewalk system met the threshold. The study confirms that deriving city-scale sidewalk availability and clear width metrics is feasible using remote sensing, but highlights that traditional methods significantly overestimate pedestrian accessibility. The significance of this work lies in providing a scalable, objective method for inventorying pedestrian infrastructure, addressing a major data gap in transportation research. By revealing the true extent of sidewalk deficiencies, the findings offer city agencies and planners a more realistic assessment of infrastructure needs. The developed prioritization methodology, which integrates spatial sidewalk data with trip data, enables efficient identification of areas requiring investment. This approach helps municipalities rectify backlogs of deteriorating pedestrian infrastructure and ensures compliance with accessibility standards, ultimately supporting safer and more inclusive urban environments.

Key finding

Accounting for static obstructions reduces the average sidewalk clear width by 22 percent and causes the median width to drop to the ADA minimum threshold, revealing that ignoring obstructions leads to a significant overestimation of sidewalk adequacy.

Methodology

dataset

Sample size: 1523

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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• signage environment