220th Street Mobile Mapping to Evaluate Americans with Disabilities Act Compliance

Tetra Tech performed a design-grade mobile mapping collection of a 0.6-mile-section of 220th Street in Edmonds, Washington.

The project allowed the city to analyze existing access ramps for compliance with the Americans with Disabilities Act (ADA), as well as to design new ramps and perform a full road pavement analysis and overlay within the section that was mapped. The federally funded project required designs to be completed in eight weeks to allow construction to begin in 2016.

To generate a full design-grade map within the required tight timeframe, Tetra Tech deployed a mobile mapping crew to collect data using the Pegasus:Two in two passes at the posted roadway speeds. We completed all data field collection as scheduled and in just half a day. We also successfully captured orthoimagery in unison with LiDAR data to aid in data extraction.

Data collected for the base map included road markings, sidewalks and ADA curb ramps, utility covers and hydrants, signal poles and equipment, utility and light poles, and street signage.

Our team began processing all mobile mapping data the day after collection occurred. Tetra Tech used the Pegasus viewer software to analyze and document current ADA compliance at street intersections, assess pavement condition, and identify ADA ramp upgrades for the project including documentation for federal audit purposes. In addition, mapping was used to analyze the corridor for compliance with ADA requirements trigged with a pavement overlay designed for the project.

Deliverables included a full topographical design base map in AutoCAD formats, planimetric mapping at 1:20 scale in AutoCAD DWG format, topographic mapping at 1 U.S. survey-foot contour intervals, and a digital terrain model at a 10-foot grid throughout the site. Our team created a pavement design report documenting pavement repair sections and overlay thickness along with a study of the existing ADA ramps, analyzing compliance and retrofit options through the project limits. The final product was a set of construction drawings and specifications to meet federal funding compliance and Washington State Department of Transportation review for construction approval. Tetra Tech successfully completed the data collection, analysis, and design for ADA ramps and pavement improvement in less than eight weeks.