Use of ArcGIS and Fuzzy Analytical Hierarchy Process for Base Condition Assessment of NMDOT Culverts

Abstract: Culverts constitute a vital portion of transportation assets that require routine inspection, maintenance, and timely repair and renewal. Variations in structural characteristics, environmental exposure, and wide geospatial distribution of these infrastructure assets, along with budget constraints, pose a significant challenge for the transportation agency. Over time, structural and non-structural defects increase the probability of culvert failure with consequences ranging from benign to catastrophic. This research investigates the baseline structural and non-structural condition of three common culvert types, as part of the Culvert Asset Management Plan (CAMP) of the New Mexico Department of Transportation (NMDOT) to support long-term risk-based asset management.

CAMP is an initializing project to support long-term risk-based asset management plans by combining assets, culverts in this case, and conditions into a single Geographical Information Systems (GIS) database. NMDOT was contracted with two public universities to collect GPS coordinates and conduct external culvert inspections. New Mexico Institute of Mining and Technology (NMT) was one of the contracted institutions. The project includes acquiring a 1.5m accuracy GPS coordinate, photographs, and an asset description including construction materials, size, number and type of openings, appurtenances, visual condition, and damage present. Inspectors were hired from the student body, with faculty providing project supervision. The CAMP project collected data during each of four summers since 2021, inventorying 51,000 culverts using handheld Trimble TDC600 GPS and a User Input Data Dictionary, developed by NMDOT to collect and define inspection information. The data was sorted into various culvert types based on the material of construction code with primary focus on Corrugated Metal Culvert (CMC), Concrete Box Culvert (CBC), and Concrete Pipe Culvert (CPC). These configurations represent a majority (approximately 82% of the CAMP database) of non-urban culvert infrastructure. Minor categories sorted include other concrete, metal, plastic, and wood culverts. These latter types were excluded for further analysis.

Fuzzy Analytical Hierarchy Process (FAHP) Pairwise Comparisons (PWC) based on expert opinion was implemented to develop weightings for selected culvert structural or non-structural defects. Data mining of the inspection inventory using pre-selected NMDOT Schema Coded Values coupled with derived FAHP weightings allowed for the development of a Base Assessment Condition (BCA) rating score for each geolocated culvert. This metric provides an assessment of the criticality of culvert condition on a relative numeric scale from good to bad and allows for phased prioritization of statewide culverts for further maintenance or replacement action. Expert consensus between each PWC criteria was evaluated using a Double Entropy Index for inter-rater agreement. Additionally, Hot Spot Analysis, using Spatial Analysis in ArcGIS Pro, helped identify statistically significant spatial clusters of high values (hot spots) and low values (cold spots) of specific defects and BCA ratings statewide and within NMDOT district boundaries.