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FHWA Highway Safety Programs

2: Assessing Factors Affecting Non-Motorized Safety

2.1 Defining the Problem

Assembled non-motorized safety data should be used to define the extent of the problems, and/or the study area, before a more detailed data analysis is conducted. Summary tables, annotated maps, and crash diagrams are useful in identifying not only crash locations but also crash trends and areas of higher risk based on similar roadway and user characteristics to those experiencing crashes. The study area may also be defined by project opportunities, such as including non-motorized safety improvement into scheduled projects (e.g., resurfacing). The study area can exist at three different scales: spot location, corridor, or network. The following information is intended to help readers identify the appropriate study area for a more detailed analysis:

Spot Locations –

A spot location problem exists where there is one location (or several unrelated locations) experiencing safety-related concerns or crashes. Spot locations may include crossings, intersections, curves, or locations of activity, such as schools or markets.

Spot Location Example: A specific trail crossing or a road crossing near an area with high pedestrian and bicycle activity.

Corridor –

A corridor problem exists when multiple locations on a segment of roadway experience safety concerns or crashes. Those safety concerns or crashes may be varied in nature or may include one or more unifying factors.

Corridor Example: A segment of rural road with limited space for non-motorized users.

Network–

The network problem exists when similar types of crashes are occurring at multiple locations on different roadway corridors, and the emerging safety concerns appear to be related in nature.

The process of reviewing the data may indicate issues associated with one or more of the study area types. If the issues and common risk factors identified through crashes encompass more than one study area, specific manageable actions or projects may be developed at the appropriate scale to address the most pressing safety concerns in each area. Jurisdictions experiencing similar crash types or issues on a larger scale (i.e., at the corridor or network level) may benefit from systemic improvements.

Network Example: An area with dispersed non-motorized activity. Consider non-motorized crashes on the roadway network in a jurisdiction.

2.2 Analyzing Data

Typically, the detailed analysis consists of two parts: an in-office analysis of data to determine the crash trends and safety issues, and a field assessment to provide a more complete understanding of the data and the factors affecting non-motorized safety.

In-office Data Review

The purpose of the in-office data review is to develop a comprehensive summary of crash types and locations that allow reviewers to identify possible crash trends and study areas for issue identification and possible countermeasure selection and implementation.The Pedestrian and Bicycle Crash Analysis Tool (PBCAT) can be used to help facilitate the crash data analysis. PBCAT is a crash-typing software that assists practitioners with analyzing crash data by creating a database containing details about crashes between motor vehicles and pedestrians or bicyclists. PBCAT can be used to identify, organize, and analyze crashes by location, type, severity, time of day, prevailing conditions, user age, and other crash-related factors that are helpful in identifying crash trends.

If multiple data sets are available, they can be used to help identify crash trends or common characteristics. For example, if crash and traffic data for non-motorized users are available, then these can be used to determine crash rates. Crash rates are the ratio of non-motorized crash frequency (in crashes per year) to exposure (the number of non-motorized users). Additional information on crash analysis procedures can be found in Road Safety Information Analysis: A Manual for Local Rural Road Owners. (17)

Assessing Conditions in the Field

Available data may not provide a complete picture of conditions and behaviors that affect non-motorized user safety. Crashes may go unreported or reported crashes may be infrequent or scattered. A field assessment should be conducted to investigate crash trends identified in the in-office analysis and identify additional factors that may contribute to crashes involving non-motorized users. Conditions to be reviewed as part of a field visit include the following:

  • Presence, visibility, and condition of signs and pavement markings that pertain to non-motorized users.
  • Expectancy of non-motorized users by a motorist.
  • Space, or lack thereof, shared by motorized and non-motorized traffic.
  • Visibility of all road users with respect to each other.
  • Quality and conditions of facilities used by non-motorized users.
  • Speed of motorized traffic.
  • Volume of motorized and non-motorized traffic.
  • Composition of traffic (for example trucks, recreational vehicles, etc.).
  • Presence and quality of street lighting.
  • Conspicuity of crossings and motorist yielding to pedestrians or cyclists at crossings.

Local practitioners may engage a group of stakeholders to investigate conditions in the field. There are two basic types of field assessments for investigating non-motorized safety: walkability/bikeability assessments and road safety audits.

Walkability and Bikeability Assessments

Walkability and bikeability assessments serve to identify the characteristics and conditions that affect non-motorized mobility and safety. Most assessments can be conducted by a group of local stakeholders with a range of knowledge or experience. The information collected during the assessments can be used as the basis for more in-depth analysis of issues and selection of countermeasures by local practitioners. Materials to conduct walkability and/or bikeability assessments, including checklist forms, are available online.(18),(19) These checklists can be useful in providing guidance on conditions to look for during a field assessment. Published pedestrian and bicycle checklists can be modified for use with other non-motorized transportation.

Road Safety Audits

Road safety audits (RSAs) are a formal examination of an existing facility or future roadway plan/project that is conducted by an independent, experienced, and multidisciplinary team. They are a proven safety tool used to evaluate safety and to identify opportunities for improvement. RSAs involve participants walking or bicycling the study area, observing operational behaviors, talking with those who use the facilities on a regular basis, and developing a more complete understanding of the facility's existing mobility, access, surrounding land use, and operational context. RSAs can result in enhanced safety by allowing participants to carefully consider situations presented to all roadway users under variable conditions, including time of day (daylight vs. darkness), weather (e.g., clear, rain, snow, ice, etc.), peak/non-peak travel, and major events (e.g., sporting events, festivals, etc). Though RSAs consider all road users, an RSA may be initiated to specifically address non-motorized safety or crashes.

The RSA process may be employed on any type of facility and during any stage of the project development process. RSAs may be conducted proactively to identify conditions that present potential safety hazards or reactively to evaluate conditions and identify countermeasures along roadways that have exhibited a significant crash history.

Conducting an RSA usually does not require a large investment of time or money. An RSA typically takes one to three days to conduct, depending on the study area. By gaining a better understanding of the safety implications of roadway and roadside features, RSAs can be used to prioritize locations with safety concerns, helping to identify the best use for funding. Other benefits include encouraging multidisciplinary collaboration beyond the RSA and promoting a better understanding of roadway user needs and safety. RSA resources can be found on the Federal Highway Administration (FHWA) web site(20), including guidance for conducting pedestrian-(21) and bicycle-oriented RSAs to ensure that the needs of these non-motorized user groups are sufficiently considered in the RSA process.

2.3 Prioritizing Concerns

Prioritizing non-motorized safety concerns will help a local agency in addressing its most pressing safety problems. In general, safety concerns associated with frequent crashes and higher crash severity levels are given greater priority. If reliable crash data are available, prioritization can be based on total crash frequency or crash rate (if non-motorized traffic volume data are available). Locations or crash types with the higher crash frequency or crash rate will have a higher priority.

When reliable crash data are not available, the likely frequency and severity of crashes associated with each safety concern can be qualitatively estimated and used to prioritize locations. Expected crash frequency can be qualitatively estimated on the basis of exposure (i.e., the number of non-motorized users that would likely be exposed to the identified safety issue) and probability (i.e., the likelihood that a crash would result from the identified safety issue). Expected crash severity can be qualitatively estimated on the basis of factors, such as anticipated motor vehicle speeds.

These two risk elements (frequency and severity) are then correlated to obtain a qualitative risk assessment ranging from lowest to highest, as shown in Table 4, which can assist in prioritization of non-motorized safety concerns. For example, potential crash severity can be related to potential crash frequency as presented in Figure 2. A similar categorization can be considered for crash frequency correlated with non-motorized traffic volumes.

Table 4. Prioritization Matrix.

POTENTIAL
CRASH FREQUENCY
POTENTIAL CRASH SEVERITY
Minor Injury Moderate Injury Serious Injury Fatal
Frequent High High Highest Highest
Occasional Moderate Moderate High Highest
Infrequent Low Low Moderately High
Rare Lowest Low Moderate High

This qualitative assessment should be conducted by individuals who are familiar with the factors that affect crash frequency and severity. Local agencies should consult an engineer or other transportation professional when considering safety improvements. The State DOT and the LTAP or TTAP can provide assistance when assessing the risk of non-motorized users.