The 23 CFR 924 provides only general guidance on how safety data should be used; it does not provide details on specific data elements (1). While MIRE provides a comprehensive listing of roadway and traffic data elements, it may not be feasible for States to collect all of the 200+ MIRE elements and integrate them into their existing programs. State and local departments of transportation (DOTs), particularly highway safety agencies, are facing increasing demands and decreasing resources.
In order to address the States’ safety data improvements challenges, the FHWA held a series of information gathering sessions and convened a Technical Working Group (TWG) to determine the roadway and traffic data elements that States should be collecting, what States are capable of collecting given the current economic environment, and the importance of using roadway and traffic data in the safety analysis process. Based on these efforts, a set of elements was determined to be the fundamental roadway inventory data elements necessary to support a State’s HSIP. This set of data elements is hereafter referred to as the Fundamental Data Elements for HSIP (FDE/HSIP). These are based on the elements needed to apply HSM roadway safety management (Part B) procedures using network screening analytical tools (such as SafetyAnalyst), are a subset of MIRE, and duplicate many of HPMS full extent elements that States are already required to collect on Federal-aid Highways. The FDE/HSIP are comprised of roadway segment, intersection, and ramp elements as shown in Table 2.
Table 2. FDE/HSIP Elements
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FDE/HSIP Elements |
Definition |
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Roadway Segment |
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Segment ID* |
Unique segment identifier. |
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Route Name* |
Signed numeric value for the roadway segment. |
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Alternate Route Name* |
The route or street name, where different from route number. |
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Route Type* |
Federal-aid/NHS route type. |
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Area Type* |
The rural or urban designation based on Census urban boundary and population. |
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Date Opened to Traffic |
The date at which the site was opened to traffic. |
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Start Location* |
The location of the starting point of the roadway segment. |
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End Location* |
The location of the ending point of the roadway segment. |
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Segment Length* |
The length of the segment. |
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Segment Direction |
Direction of inventory if divided roads are inventoried in each direction. |
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Roadway Class* |
The functional class of the segment. |
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Median Type |
The type of median present on the segment. |
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Access Control* |
The degree of access control. |
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Two-Way vs. One-Way Operation* |
Indication of whether the segment operates as a one- or two-way roadway. |
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Number of Through Lanes* |
The total number of through lanes on the segment. This excludes turn lanes and auxiliary lanes. |
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Interchange Influence Area on Mainline Freeway |
The value of this item indicates whether or not a roadway is within an interchange influence area. |
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AADT* |
The average number of vehicles passing through a segment from both directions of the mainline route for all days of a specified year. |
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AADT Year* |
Year of AADT. |
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Intersection ID |
A unique junction identifier. |
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Location |
Location of the center of the junction on the first intersecting route (e.g., route-milepost). |
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| Intersection Type | The type of geometric configuration that best describes the intersection/junction. | |
| Date Opened to Traffic | The date at which the site was opened to traffic. | |
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Traffic Control Type |
Traffic control present at intersection/junction. |
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Major Road AADT |
The Annual Average Daily Traffic (AADT) on the approach leg of the intersection/junction. |
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Major Road AADT Year |
The year of the Annual Average Daily Traffic (AADT) on the approach leg of the intersection/junction. |
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Minor Road AADT |
The Annual Average Daily Traffic (AADT) on the approach leg of the intersection/junction. |
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Minor Road AADT Year |
The year of the Annual Average Daily Traffic (AADT) on the approach leg of the intersection/junction. |
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Intersection Leg ID |
A unique identifier for each approach of an intersection. |
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Leg Type |
Specifies the major/minor road classification of this leg relative to the other legs in the intersection. |
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Leg Segment ID |
A unique identifier for the segment associated with this leg. |
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Ramp ID* |
An identifier for each ramp that is part of a given interchange. This defines which ramp the following elements are describing. |
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Date Opened to Traffic |
The date at which the site was opened to traffic. |
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Start Location |
Location on the roadway at the beginning ramp terminal (e.g., route-milepost for that roadway) if the ramp connects with a roadway at that point. |
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Ramp Type |
Indicates whether the ramp is used to enter or exit a freeway, or connect two freeways. |
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Ramp/Interchange Configuration |
Describes the characterization of the design of the ramp. |
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Ramp Length |
Length of ramp. |
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Ramp AADT* |
AADT on ramp. |
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Ramp AADT Year |
Year of AADT on ramp. |
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*Highway Performance Monitoring System full extent elements required on all Federal-aid highways and ramps located within grade separated interchanges, i.e., NHS and all functional systems excluding rural minor collectors and locals.
The TWG determined that a primary goal should be to collect these 38 FDE/HSIP on all public roads. However, if a State does not have the resources to undertake the collection of all FDE/HSIP on all public roads, it is recommended as a first priority that these elements be collected on all Federal-aid highways. Federal-aid highways comprise approximately 25 percent of the Nation’s roadways and account for approximately 75 percent of fatalities (5,6). By collecting data on Federal-aid highways, States will be targeting the roadways on which a large portion of crashes occur.
Once the FDE/HSIP are collected on Federal-aid highways, States should collect the FDE/HSIP on non-Federal-aid highways. If collecting these data along all non-Federal-aid highways at one time is not feasible, the State should determine a methodology for prioritizing its collection efforts, which could be based on the following:
- Urban or rural.
- County/District.
- Functional class.
- Traffic volume.
These are just examples; each State should determine which methodology is most appropriate for its individual circumstances. A data dictionary of the elements, including the corresponding MIRE element(s), is included in Appendix A.