Enhancing Safety and Operations at Complex Interchanges With Improved Signing, Markings, and Integrated Geometry

Jackson, Steven; Katz, Bryan; Kuznicki, Scott; Kissner, Erin; Kehoe, Nicholas; Miller, Sheryl · 2018 · ROSA P / United States. Department of Transportation. Federal Highway Administration. Office of Safety

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Summary

This study addresses the safety and operational challenges posed by complex highway interchanges, which have proliferated to meet increasing traffic demand but impose high cognitive workloads on drivers. As roadway designers incorporate additional lanes, preferential lanes, and multilane exits, the resulting geometric complexity often requires drivers to perform multiple navigation tasks within short distances and time intervals. The research aimed to develop evidence-based recommendations for signing, delineation, and geometric design to reduce driver workload and improve safety at these critical locations. The methodology combined a comprehensive review of existing design practices with empirical data collection. Researchers first identified attributes contributing to interchange complexity and evaluated current geometric, signing, and marking practices across multiple U.S. jurisdictions. To assess driver behavior, the study employed two primary experimental approaches: a driving simulator study and a field study. The simulator study investigated driver performance across different interchange layouts and signing alternatives, measuring accuracy, unsafe lane changes (ULCs), and lane selection decisions. The field study involved video analysis of real-world driving behaviors at four complex interchange sites in Orlando, Atlanta, Minneapolis, and Olympia, capturing common exiting driver behaviors and potential conflicts. Key findings revealed significant inconsistencies in current practices, particularly regarding option lane signing, arrow design, and pavement markings, which often fail to align with driver expectations. Simulator results indicated that specific signing alternatives and geometric layouts significantly influenced driver accuracy and the frequency of unsafe lane changes. For instance, certain guide sign configurations reduced decision errors compared to others. Field observations confirmed that drivers frequently struggled with complex lane reductions and ambiguous exit signage, leading to erratic maneuvers. The study identified six categories of "treatments" or recommendations to address these issues. These include optimizing ramp terminal arrangements, standardizing guide sign legend arrangements and panel configurations, improving sign placement and the use of arrows/distances, enhancing delineation for exiting and special-use lanes, and refining lane-reduction methods and signing. Additionally, the study recommended implementing Traffic Control Devices (TCDs) education and design review workshops to ensure consistent application of these best practices. The significance of this work lies in its provision of actionable, research-backed guidelines for transportation professionals and state departments. By addressing the interrelationships between geometric design, traffic control devices, and human factors, the recommendations aim to standardize practices and reduce the cognitive burden on drivers. The findings offer a framework for designing complex interchanges that are more intuitive and safer, ultimately improving mobility and reducing crash risks associated with navigation errors at high-complexity junctions.

Key finding

Improved guide signing and geometric design treatments significantly increased driver decision accuracy and reduced the time required to select appropriate exit lanes at complex interchanges.

Methodology

mixed_methods

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• signage environment
• intersection design
• perceptual countermeasures
• rail grade crossings
• work zones