This report documents the long-term performance of 89 railway/highway at-grade crossings in Kentucky and adjacent states that contain asphalt underlayment underneath the ballast. Asphalt underlayment increases load carrying capacity for trains and highway vehicles while enhancing the support structure’s waterproofing and confinement. The asphalt underlayment crossings studied were installed at sites that had historically exhibited poor performance and short service lives. Most of the crossing sites evaluated were 10-15 years old; however, their ages ranged up to 30 years. All of the crossings investigated have shown excellent performance since the installation of asphalt underlayments. No crossing failures, such as excessive settlement or mud pumping, have been noted, and the service lives of the crossing surfaces have been significantly improved. Detailed results from periodic inspections are included. A literature survey focuses on eleven public agencies and railroad companies that implement asphalt underlayments. Most of these entities install asphalt underlayments at heavy traffic/tonnage crossings that have routinely shown evidence of weak support leading to inferior performance. This survey, along with the empirical results of this study, indicates that asphalt underlayment, irrespective of material used on crossing surfaces, extends the service life of crossings and improves their performance.

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