How Data is Helping Communities Prioritize Vision Zero Strategies and Funding
As more U.S. cities are adopting Vision Zero goals and principles, they are digging into data more fully to better understand what’s happening where and why and when and to whom. Armed with facts and a more nuanced understanding of the problem, Vision Zero leaders are better equipped to acknowledge and address the underlying causes of traffic deaths and severe injuries. This leads to better analysis and, in some cases, questioning of long-held assumptions about factors such as street design, speeds, and policies that influence culture and behavior.
In this process, development of the High Injury Network (HIN), or the mapping of corridors where high numbers of people have been killed and severely injured in traffic crashes, is proving to be an important Vision Zero tool. This approach is helping city staff focus limited resources on the most problematic areas, while also building greater public and political buy-in for changes.
The Vision Zero Network recommends that all Vision Zero cities research and adopt a High Injury Network, and focus resources on the corridors identified.
Vision Zero communities have found that developing an HIN helps identify where crashes occur repeatedly and why, strengthens multi-departmental collaboration, and affords the opportunity to prioritize scarce funding in areas where it’s needed most. In addition, it builds understanding among decisionmakers, including elected officials, of what’s needed and where so that funds can be invested in the areas that are most impacted by death and injury.
What is an HIN?
San Francisco was the first city to develop the HIN framework and create the title. Staff from San Francisco’s Public Health Department and Municipal Transportation Agency were working in 2013 with other agencies on a campaign to improve pedestrian safety in the city, called WalkFirst. Data from police reports showed that in a 5-year period, pedestrians in San Francisco were injured at more than 1,700 intersections in the city. Through its WalkFirst project, city staff developed its first HIN to connect these intersection-level injuries to their adjacent street segments, with the goal of better assessing patterns across the city. This analysis led to the realization that 6% of street miles in San Francisco accounted for 60% of severe and fatal pedestrian injuries.
San Francisco officially adopted Vision Zero in 2014, and as part of that effort, staff decided to build onto the pedestrian HIN to research the same data for people bicycling and driving. Staff ultimately combined all layers to create the Vision Zero HIN in 2015. In this, they found that 12% of city street miles contributed to 70% of fatal and severe injuries among all road users. In short, the assessment was a game changer to identify leading problem areas.
“Creation of HIN helped the City avoid a whack-a mole approach – or one intersection at a time – to understand patterns of death and serious injury and inform more sustainable, more effective engineering measures to ultimately save lives,” says Megan Wier, Director of the Program on Health, Equity, and Sustainability for San Francisco’s Department of Public Health.
To learn more about the specific data used to develop San Francisco’s HIN, go to www.transbasesf.org.
How to Get Started?
Staff in San Francisco shares recommendations on how to get started on creating an HIN:
- Identify injury/fatality data sources, by severity: Police, Medical Examiner, EMS, Hospital
- Develop relationships and points of contact with agencies, including formal datasharing agreements as needed
- Access data and map deaths and injuries – ideally give more weight to more severe injuries
- Identify corridor and area patterns in the injury data – ideally beyond the intersection
- Engage with data partners and key city and community stakeholders to interpret the findings, clarify limitations, and discuss how they can inform your Vision Zero initiative
Many other cities have followed San Francisco’s lead in creating HINs, particularly to lay a foundation for their Vision Zero efforts.
Trends in HIN development among Vision Zero cities include the following:
- A relatively small percentage of cities’ street networks account for a disproportionately higher portion of traffic deaths and serious injuries;
- Many of the streets in the HIN are arterials, or streets that carry higher volumes of vehicles at higher speeds; and
- Many HIN streets are located in low-income, communities of color, and/or low mobility communities.
Evolution of San Francisco’s HIN
| High Injury Network | HIN Streets | Injuries/ Fatalities | Communities of Concern (CoC) |
| 2015 | 12% of city street miles | 70% of severe injuries and fatalities | |
| 2017 update | 13% of city street miles | 75% of severe injuries and fatalities | 51% of HIN is located within CoC |
After releasing its original HIN in 2015, San Francisco updated it in 2017 to add hospital injury data to compliment police injury data, thereby including injuries not previously reported in police reports. Use of the hospital data allowed a deeper assessment of the severity of injuries and a greater focus on the high numbers of people seriously injured and killed, to be consistent with the goals of Vision Zero. Use of the hospital data also showed better the impact of traffic deaths on vulnerable communities such as people walking and biking, and people of color. San Francisco’s 2017 update to its HIN assessment revealed that 13% of city street miles contribute to 75% of severe injuries and fatalities for all modes, and half of the HIN falls within the city’s most vulnerable communities.
In another important development that is influencing Vision Zero strategies nationwide, San Francisco overlaid the HIN with areas they identify as Communities of Concern. These communities are identified as having a concentration of vulnerable residents including low income residents and people of color among others (see picture below). The overlay allows staff to measure the impact of fatal and serious traffic crashes on certain segments of the population, such as low-income or low-mobility communities. Data shows that 51% of the HIN identified in San Francisco is located within the city’s most vulnerable communities.
How the HIN is Used
San Francisco is using data in the HIN to inform decisions about safe street improvements, education, and police enforcement. Corridor data has helped the San Francisco Municipal Transportation Agency (SFTMA) create actionable strategies to make safety changes on the streets that need them most. The HIN “helps staff better dissect and analyze safety problems by transportation mode and target safety countermeasures to match,” says Tom Maguire, Director of SFMTA’s Sustainable Street Division. For example, a street with a high number of injury crashes between people driving and bicycling may merit a physically separated bikeway to provide better safety and predictability for all road users. And a corridor with a high number of pedestrian injuries and high speeds may warrant traffic calming measures to lower driver speeds. Doing this work at the corridor level brings big benefits to address the root causes of the problems and have a greater impact.
Denver, Colorado High Injury Network
| High Injury Network | HIN Streets | Serious Injuries/ Fatalities | CoC |
| October 2017 Action Plan | 5% of city street miles | 50% of traffic fatalities | 38% traffic deaths are in CoC and 44% of ped deaths |
One of Denver’s core values behind Vision Zero is to focus city efforts on the most dangerous streets and in the most vulnerable communities. Development of the HIN helps staff to do this. Denver’s mayor announced the city’s commitment to Vision Zero in 2016, and Denver staff looked at HIN examples in San Francisco and Los Angeles to guide its efforts.
Staff analyzed crashes in the Denver crash database for the years 2011-2015 by mode to produce three distinct HINs: pedestrian, bicycle, and motor vehicle, as in San Francisco’s efforts. Staff detailed crashes for each mode to better understand the causes of crashes and, ultimately, develop appropriate solutions. The Vision Zero project team also assigned weights representing the severity of the crash for fatal and injury crashes, but not for non-injury crashes. Data sources used to create the HIN included the City of Denver Public Works (DPW), Colorado Department of Transportation (CDOT), and Denver Police Department (DPD).
Denver aimed to prioritize equity within its HIN from the beginning. The city’s Vision Zero Action Plan states, “Implementation of the Action Plan will be informed by our goal to reduce geographic disparities in traffic injuries and deaths across the city.” Denver’s Public Health Department identified Communities of Concern (CoC), or areas with low income and education levels, and high concentrations of seniors among other factors (see image below). The CoC areas account for around 30% of the area of Denver, but 38% of all traffic deaths and 44% of pedestrian deaths.
How the HIN is Used
Denver developed and shared its HIN in October 2017 as part of the Vision Zero Action Plan. Staff will begin using the HIN in 2018 to look at micro-level crash data to identify issues and appropriate countermeasures, then create a project pipeline to inform the allocation of funds in the city’s 2019 budget. In this process, they expect projects in the HIN and Communities of Concern to be prioritized highest.
For Denver and other Vision Zero cities, it comes down to using the HIN to best prioritize scarce resources amongst many needs and completing interests.
“We have over 1,300 traffic signals, about 4,000 lane miles and countless traffic signs in the City and County of Denver,” says David DiGiacamo, Senior Engineer in Denver’s Public Works Department. “Developing an HIN helps focus our safety efforts to a handful of corridors where we know we can see the most safety benefits with our limited resources.”
“Together the City’s HIN and COC provide a proactive approach to allocating resources to the areas of greatest need. This will be a guiding framework for prioritizing how we work.” -Michele Shimomura, Public Health Manager in Denver’s Department of Public Health and Environment adds,
San Jose, California High Injury Network
| Priority Safety Corridors – Research Period | HIN Streets | Serious Injuries/ Fatalities | CoC |
| 2010-2014 | 3% of city street miles | 50% of traffic fatalities | 14% |
| 2012-2016 | 3% of city street miles | 33% of traffic fatalities & serious injury crashes |
In San Jose, California, the Department of Transportation conducted an analysis of traffic collision records from a 5-year period and identified 14 “Priority Safety Corridors” as part of its 2015 Vision Zero Action Plan. These corridors are long segments of city streets and expressways with the highest frequency of fatal and severe injury collisions for people driving, walking, and biking. Their research found that 3% of the city’s street network accounted for slightly more than 50% of the fatal traffic crashes.
Staff updated their data in 2016, adding 9 miles of roadways as Priority Safety Corridors and determined that 3% of the street network was contributing to 33% of fatalities and serious injuries in the city. As part of this data research, staff also determined the most dangerous behaviors contributing to the crashes along the Priority Safety Corridors.
How the HIN is Used
Staff in San Jose used data from the Priority Safety Corridors to work with surrounding communities and conduct safety assessments for each of the corridors. Each of the assessments includes recommendations focused on engineering measures to help reduce vehicle speeds, minimize traffic conflicts, and create a safer environment for people walking. Assessments also included recommendations for enforcement and traffic safety education.
The identified engineering improvements helped city staff apply for and win more than $25 million in grant funds for several Priority Safety Corridors. These funds were used in addition to city funds for several projects, many of them now in the design phase.
Other Examples of High Injury Networks
Chicago, Illinois
| High Crash Corridors & High Crash Areas | HIN Streets | Serious Injuries/ Fatalities | CoC |
| 2010-2014 | 20% of the city’s geographic area | 36% of traffic fatalities |
Chicago’s High Injury Network identifies high crash corridors and neighborhoods.
Philadelphia, Pennsylvania
| High Injury Network | HIN Streets | Serious Injuries/ Fatalities | CoC |
| 2012-2016 | 12% of city street miles | 50% of traffic fatalities and severe injuries |
Philadelphia’s High Injury Network is comprised of the corridors on which fatal and serious injury crashes for people driving, walking, and biking, occur with the most frequency. A weight was placed on crashes resulting in the death or a severe injury of someone walking or biking to protect the most vulnerable users.
Los Angeles, California
| High Injury Network | HIN Streets | Serious Injuries/ Fatalities | CoC |
| 2009-2013 | 6% of city street miles | 65% of traffic fatalities and severe injuries for people walking and biking |
Los Angeles’ High Injury Network identifies intersections and corridors on which fatal and serious injury crashes for people walking and biking occur with the most frequency. Like in Philadelphia, a weight was placed on crashes resulting in the death or a severe injury of someone walking or biking to protect the most vulnerable users. Los Angeles also developed an intersection score for intersections within the HIN to help prioritize future engineering improvements. These factors included crash severity, vulnerability, social equity, and geography among others.
Sacramento, California High Injury Network
| High Injury Network | HIN Streets | Injuries/ Fatalities | CoC |
| 2009-2015 | 14% of city street miles | 77% of traffic fatalities and all injuries | 35% |
Sacramento’s High Injury Network identifies corridors with the highest levels of fatal and serious crashes for pedestrians, bicyclists, and drivers, and the burden traffic crashes have on vulnerable populations, such as seniors and Disadvantaged Communities. According to the draft Vision Zero Action Plan, understanding the patterns “helps the city be proactive in identifying high-risk locations.”
Conclusion
It is a traditional practice for cities to try to spread resources evenly across communities, but Vision Zero principles and the use of HIN data show that some communities are more impacted than others and deserve more attention.
As a result, HINs represent a critical tool to help cities build support for and allocate resources to the areas that need them most. The research behind the HINs also allows Vision Zero communities to identify roadway characteristics that contribute to deadly situations and to assign appropriate design solutions, or countermeasures.
Numerous benefits come with developing a High Injury Network (HIN), such as:
- Determining geographic areas where crashes are concentrated and the causes of these crashes, so that efforts can be focused on the most problematic areas and the most dangerous cause factors;
- Strengthening cross-departmental collaboration to focus street improvements, and education campaigns in the HIN; and
- Prioritizing investments, particularly important when resources are limited.
Ultimately, HIN data is only as good as it is put to use. Vision Zero is not a slogan, it is a fundamentally different way of approaching traffic safety to acknowledge traffic deaths are preventable, and to take proactive actions that prevent the loss of life and serious injury. The HIN has become a must-have resource for cities to win with Vision Zero.
*Note: “HIN for the WIN” was originally used by advocates in Los Angeles to urge the city to prioritize funding for engineering projects on LA’s High Injury Network.
Want to learn more? Check out a recorded presentation from San Francisco leaders discussing the creation and use of their HIN here.