Official Site of The State of New Jersey

Rockfall events have significantly impacted traffic conditions along this segment of the Interstate 80 (I-80) highway. Between 2003 and 2018, within the Project Area, I-80 has been fully closed at least three times due to major rockfall events. A rockfall event is defined as any documented report of rockfall or debris from the rock slopes which directly impacts the highway. This data is compiled from New Jersey State Police crash reports, New Jersey Department of Transportation (NJDOT) Division of Operations and Maintenance records, and NJDOT Department of Geology field reports.

Traffic slowdowns or partial closures have also occurred as a result of the poor conditions associated with the deteriorated rock slopes along this segment of I-80. The slopes and geology in this segment of I-80 are such that trees and shrubbery have grown in the loose, rocky soils. When subjected to heavy rainfall or snowmelt, the fast flow of surface groundwater over such terrain can erode and undermine vegetation causing it to dislodge and fall to the roadway. In addition, this high volume of groundwater often overtops the roadside barrier and can flood the roadway surface causing icy conditions or reduced lane capacity.

Gathering information on rockfall regularity and significance is often observational or anecdotal in character. Maintenance work associated with the clean-up of rockfall debris is not tracked in any formalized fashion at the local maintenance facility. However, interviews with regional maintenance staff have confirmed that they regularly pick up fallen rock material on a weekly basis within the I-80 Project Area. The standard operation consists of a “rolling closure” configuration.

Tracking rockfall events provides valuable data that validates the rating and ranking methodology employed and accepted by professionals nationally. One of the best chronicles of rockfall events directly impacting a highway is obtained from police crash records. Over 600 New Jersey State Police crash records for this section of I-80 were reviewed to identify any crash resulting from rock or natural material entering the highway from the border area. Since the standard alphanumeric coding information in a crash report is sometimes inaccurate or erroneously recorded, the written description in each record was reviewed for specific details.

Between 2001 and 2018, a total of 29 “events” directly related to rockfall activity were identified in the Project Area. These 29 events include the following:

• 14 occurrences of rocks falling and landing on the highway;
• six occurrences of a tree falling and landing on the highway;
• four occurrences of highway flooding; and
• five occurrences of highway icing.

Based on the review of New Jersey State Police crash records, no crashes resulted from flooding or icing on the highway. One crash resulted from a tree falling on the highway and 13 crashes resulted from rocks falling and landing on the highway. It is important to note that the number of crashes from rocks falling on the highway (13) does not match the number of occurrences of rocks falling as listed above (14) because not all occurrences of fallen rock resulted in crashes while other occurrences of fallen rock resulted in one or two crashes. (There were four occurrences of fallen rock that did not result in any crashes. Seven occurrences of fallen rock resulted in one crash per occurrence and three occurrences of fallen rock resulted in two crashes per occurrence.) In total, there have been 14 crashes that resulted from rockfall activity—one from a fallen tree and 13 from fallen rock. Of this total, there was one crash that resulted in one fatality and one minor injury.