VALIDITY OF GARBER MODEL IN PREDICTING PAVEMENT CONDITION INDEX OF FLEXIBLE PAVEMENT IN KERBALA CITY
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Summary
This study evaluates the validity of the Garber et al. model for predicting the Pavement Condition Index (PCI) of flexible pavements in Kerbala City, Iraq. The research addresses the need for accurate pavement maintenance management systems (PMMS) to prioritize rehabilitation strategies amidst limited funding. Specifically, it investigates whether the Garber model, originally developed from data on 20 pavement sections, can accurately estimate PCI values for urban arterial and collector roads in a different environmental and traffic context. The methodology involved collecting data from 44 road sections in Kerbala. Three key variables required for the Garber model were determined: pavement age (AGE), average daily traffic (ADT), and structural number (SN). ADT was derived from video-recorded traffic counts, converting vehicle volumes into passenger car units using standard conversion factors. SN was determined through destructive field testing (core sampling) and laboratory analysis. Core samples from surface and base layers underwent Marshall Stability Tests to determine layer coefficients and thicknesses, which were then used to calculate the structural number. The Condition Index (CI) predicted by the Garber model was compared against PCI values generated by the PAVER 6.5.7 software, which is based on ASTM D 5340 distress surveys. Statistical analysis, including paired t-tests, was performed to assess the significance of differences between the two datasets. The results indicate that the Garber model significantly overestimates pavement condition compared to the PAVER software. The mean CI from the Garber model was 87.04, whereas the mean PCI from PAVER was 79.50. A paired t-test revealed a statistically significant difference between the two values (p = 0.000), leading to the rejection of the null hypothesis. The correlation coefficient between the model’s predictions and the observed PCI was 0.771. The authors attribute this discrepancy to differences in environmental conditions, loading types, materials, and layer thicknesses between the original Garber dataset and the Kerbala study area. Additionally, low structural numbers relative to pavement age in many sections exacerbated the divergence. The study concludes that the Garber et al. model is not valid for predicting PCI values in Kerbala City without modification. The significant deviation suggests that the model requires calibration or that a new model should be developed using local data to account for specific regional variables. This finding highlights the importance of localizing pavement prediction models to ensure accurate maintenance planning and resource allocation.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-20 |
| archive | success | canonical_url | — | — | 1 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-20 |
| chunk | success | chunk | — | — | 1 | 2026-06-20 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-20 |
| promote | success | — | — | — | 1 | 2026-06-20 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-20 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
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