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Model Minimum Inventory of Roadway Elements—MMIRE

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PROPOSED MMIRE ELEMENTS

The proposed listing of MMIRE elements is presented in the matrix in Appendix B. For clarity of presentation, the project team divided the listing into the following categories and subcategories. Individual elements/variables are then listed under each subheading.

As shown, the descriptors are categorized into three basic groups—roadway segment descriptors (e.g., begin and end route milepost, number of lanes, AADT), roadway segment alignment descriptors (e.g., degree of curve, percent grade), and road junction descriptors (e.g., type of junction, approach traffic volume, presence of protected left turn phasing). While most current inventory systems are divided into these three basic file types, relational databases would allow the data to be stored in alternative ways. Thus, the categorization is logic driven and used for explanation purposes rather than a prescription for file layouts.

The matrix in Appendix B includes the following information:

• Column A—The MMIRE Data Elements. The elements are organized into the subfiles indicated above.
• Column B—Definitions of MMIRE Data Elements.
• Column C—Project Team’s Recommended Priority. For each data element, the project team has provided a proposed priority—1^st or 2^nd. This priority is based on a combination of factors including the requirements of the four major data sources and tools noted above and the team’s knowledge of current and expected future analysis and tool needs. Note that other elements were considered both by the project team prior to the workshop and by the review team at the workshop, but are not included in the final proposed list of elements since no strong current or future association with safety analysis or management could be identified.
• Column D—Ease of Data Collection. For each data element, the project team has provided an estimate of the ease of data collection for that variable—easy, moderately difficult, difficult. This estimate is based a number of factors including whether a data item is likely to be already collected (e.g., is an HPMS-required universe variable) and the team’s knowledge of State agencies’ attempts to collect the data. An asterisk (*) indicates that a proposed new data collection system is currently being developed to assist in the compilation of these elements (e.g., the FHWA Digital Highway Measurement System⁽⁶⁾).
• Columns E-I—Presence of Each Data Element in the Five Basic Data Sources. Note that the level of requirement is coded for each column (e.g., for HPMS, whether the element is required in the Universe File or in the Sample File.)

PROPOSED MMIRE ELEMENT CODING

Appendix C contains the proposed coding for each of the proposed MMIRE elements. The element name, definition, attributes (i.e., proposed coding), and source of coding is presented. When similar coding was found in the major sources, "All Sources" is noted. In many cases, "Project team" indicates coding for a new variable proposed by the project team. In other cases, it indicates that no coding was found for an element in the major sources, and the coding was based on the project team’s knowledge of coding in existing State inventory files.

ADDITIONAL SAFETY VARIABLES IN THE NATIONAL BRIDGE INDEX AND USDOT NATIONAL HIGHWAY-RAIL CROSSING INVENTORY

The MMIRE matrix in Appendix B includes reference to both the National Bride Index¹⁰ and the USDOT National Highway-Rail Crossing Inventory¹¹. Both these inventories contain multiple variables, some of which are related to safety and some related to nonsafety usage (e.g., bridge strength ratings). At the request of and with the input of a State DOT workshop participant, a listing of those elements in each file that are most related to safety analyses are included for information in Appendix D.

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