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Assessing Network Connectivity, Vulnerability and Resilience

A Case Study from Southern California

Utah Model User’s Group

Zeina Wafa

January 22nd , 2026

Cambridge Systematics, Inc.

presented to

presented by

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Agenda

  • Introduction
  • Compliance Assessments
    • Intersection Density
    • Distance to Exits and Shelters
    • Emergency Response Times
    • AB 747: Average Evacuation Time
    • SB 99: Stranded Zones Analysis
  • Regional Evacuation Analyses
  • Emergency Bypass Study

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Introduction

  • 197 natural disaster events in California since October 1991, impacting all 58 counties.

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  • Similar vulnerabilities in Utah due to geography and three major faults: Wasatch, Hurricane and Needles.

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Introduction

  • San Bernardino County Emergency Evacuation and Network Resilience Study
  • Funded by the FY 2023-24 Caltrans Sustainable Transportation Planning Grant Program
  • Resilience planning efforts are important because “…existing hazards, such as landslides, flooding, and wildfire risks, and are expected to strain the transportation networks and communities of both San Bernardino and Riverside Counties.”

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Introduction

Senate Bill 99

Mandates that cities and counties review their Safety Elements to identify residential developments in hazard zones with only one evacuation route.

Assembly Bill 747

Requires local jurisdictions to identify and analyze the capacity, safety, and viability of evacuation routes under potential emergency scenarios, like wildfires or tsunamis.

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Compliance Assessments

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Intersection Density

  • Measure of network connectivity.

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  • Requires a network more detailed than a model network.

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  • Can be measured as number of intersections per mile of street network for each TAZ.

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Distance to Exits

  • Identifies the shortest distance from every TAZ centroid to exit city boundaries.

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  • Requires a network more detailed than a model network.

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  • Additional measure of network connectivity and vulnerability.

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Distance to Shelters

  • Identifies the shortest distance from every TAZ centroid to emergency shelters.

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  • Requires a network more detailed than a model network.

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  • Additional measure of network connectivity and vulnerability.

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Emergency Response Times

  • Identifies the shortest peak travel time from every fire station to every TAZ.

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  • Additional measure of network connectivity and vulnerability.

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  • Uses congested travel times off the model network.

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Average Evacuation Time

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AB 747: Average Evacuation Time

  • Identifies vehicular demand by time of day.
  • Identifies evacuation network capacity (vehicles/hour) depending on location of hazard.
  • Calculates average evacuation time (minutes) as the ratio of demand to capacity.

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Scenario

Evacuation Demand (vehicles)

Evacuation Capacity (vehicles/hour)

Evacuation Times (minutes)

AM Earthquake

31,541

34,130

55.45

AM Flooding

31,541

20,480

92.41

PM Flooding

47,206

20,480

138.30

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SB 99: Stranded Zone Analysis

  • Identifies combinations of parcels that have one ingress/egress which may be stranded in an emergency.

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  • Uses the latest Open Street Map (OSM) network.

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  • Identifies locations where network redundancies should be considered.

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Regional Evacuation Analyses

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Improvement Project Identification

    • Disaster risk
    • Safety effects
    • Development feasibility

Qualitative

    • Throughput
    • Evacuation time
    • Emergency response time

Quantitative (using the model)

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SBCTA Emergency Bypass Study

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Case Study: Cajon Pass

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Case Study: Cajon Pass

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Thank You for Your Time

Please reach out with additional questions or queries.

Zeina Wafa

zwafa@camsys.com

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