From "warning" to "guidance": design of a closure control zone for eight-lane freeways and evaluation of its regulating effects on driving behavior.

INTRODUCTION

Emergency closures of eight-lane freeway mainlines require vehicles to execute multiple successive lane changes to detour, a maneuver that is more complex and risky than on narrower freeways. Current standards lack tailored control zone designs and empirical evidence for such scenarios.

METHODS

To address the lack of standards for eight-lane freeway full closures, a control zone was designed based on the principle of "active guidance, graded transition, and terminal enforcement." Recognizing the complexity of multiple mandatory lane changes, two warning signs were developed: a basic version and an enhanced version adding the advisory "Merge Right for Detour." A 2 × 2 factorial driving simulator experiment (sign type × weather condition) involving 30 licensed drivers was conducted to evaluate lateral and longitudinal driving behavior.

RESULTS

The enhanced "Warning & Advice" sign consistently improved driving performance. It prompted earlier lane-change initiation (by 966 m in clear weather and 610 m in dusty weather) and reduced the aggressiveness of three successive lane changes (by 35.8, 23.8, and 23.5% in clear weather; the first two by 49.3 and 31.3% in dusty weather). Longitudinally, it decreased maximum deceleration aggressiveness by 21.7% (clear) and 25.1% (dust) and improved deceleration smoothness by 16.0 and 25.4%, respectively. Dusty weather amplified these benefits, indicating a synergy between environmental caution and explicit guidance.

DISCUSSION: Incorporating actionable advice into warning signs optimizes driver decision-making and shifts the control strategy from passive "warning" to active "guidance." The findings provide an empirical basis for the design of closure control zones and demonstrate that well-designed information can compensate for environmental uncertainty, thereby enhancing safety in complex multi-lane closures.