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Like many communities, the Bay Area city of Lafayette, Calif., wants to alleviate traffic congestion, so the city partnered with engineering firm Arup on a Downtown Congestion Study. First, Arup set out to summarize the root causes of existing congestion and forecast future conditions. The city had previously measured congestion using surveys and traffic counters, but these data sets did not explain why traffic congestion was occurring. The raw counts did not reveal trip origins and destinations, and the regional travel demand model was too broad for analyzing specific roadways.

At the project’s outset, Arup and the City of Lafayette identified the different groups that could be contributing to the downtown area’s congestion. They focused on public transit-bound commuters driving to the Lafayette BART station, drivers accessing State Route 24 (SR24), students getting dropped off at nearby schools, and shoppers heading to downtown retail stores. They used StreetLight InSight Origin/Destination with Middle Filter Travel Metrics to get a holistic overview of these different groups’ trip volumes and behavior. The metrics helped reveal that improving the flow of through-travelers using SR 24 would do the most to mitigate traffic.

StreetLight Data is a San Francisco-based technology firm and mobility analytics company that brings real-world travel patterns to light. It transforms the massive amount of geospatial data produced by mobile devices, including mobile phones, GPS devices, connected cars, fitness trackers, and commercial fleet management systems. These devices ping cell towers and satellites, creating records of their locations. StreetLight Data transforms trillions of these anonymized records into useful information with its proprietary, algorithmic processing engine, RouteScience.

Transportation experts, urban planners, and commercial property developers can access StreetLight Data’s Metrics in minutes via an online platform, StreetLight InSight, for running metrics directly from a computer’s internet browser. The StreetLight InSight platform lets customers ask and answer specific questions about travel patterns.

With a full understanding of trip origins and destinations during peak congestion times, the city and Arup could clearly communicate travel patterns and calibrate their travel traffic simulation models for analyzing future conditions. Next, Arup will help the city prioritize the policy and infrastructure improvements that will do the most to ameliorate traffic in downtown Lafayette. The Downtown Congestion Study is still ongoing, and final recommendations will be subject to approval by the city.

Working from their prior understanding of the downtown corridor’s traffic flows and the groups most likely to impact congestion, Arup and the city first defined their analysis zones (see Figure 1) and the specific trip types that they wanted to study:

  • External-External Trips or “Through Trips,” which pass through Lafayette without stopping;
  • External-Internal Trips or “Incoming Trips,” which originate outside of and end within Lafayette zones;
  • Internal-External Trips or “Outgoing Trips,” which originate within but end outside of Lafayette zones;
  • Internal-Internal Trips or “Local Trips,” which originate and end inside of Lafayette.

Figure 2: Relative share of through trip routes

StreetLight InSight Origin/Destination with Middle Filter Travel Metrics revealed the relative volume of each trip type through the downtown corridor as a percentage of the total trips, as well as the relative volume of each trip type along specific routes. These are some of the most important findings:

  • nearly 30 percent of trips in the downtown area are External-External Through Trips;
  • about 39 percent of those External-External Trips used Moraga Road, and 60 percent of those trips using Moraga Road proceeded to either SR24 West or to Mount Diablo Boulevard (see Figure 2); and
  • more than 70 percent of Incoming Trips with destinations in downtown Lafayette’s retail zones travel on SR24 from origins outside of Lafayette.

These observations, which were backed up by data collected through surveys and traffic counts, helped Arup identify the most significant factor for resolving congestion — the connections to SR24 ramps on Moraga Road, Mount Diablo Boulevard, and 1st Street.

Information provided by StreetLight Data (www.streetlightdata.com).