Proactive Strategy for Variable Speed Limit Operations on Freeways Under Foggy Weather Conditions

Abstract

Adverse weather conditions are a critical external factor that threaten traffic safety on freeways. Variable speed limit (VSL) operations can be used as a traffic management tool to harmonize vehicle speed and reduce the likelihood of crashes during adverse weather conditions. This paper proposes a novel VSL operations strategy based on the prediction of weather and traffic conditions, referred to as a proactive VSL operations strategy. The k–nearest neighbors ( k-NN) statistic was used to predict weather and traffic conditions. VSL operations logic, which used visibility distances and safe stopping distances obtained from road weather information systems and average speeds obtained by vehicle detection systems, was developed. The proposed methodology is focused on the restricted visibility distance resulting from foggy weather conditions on freeways. A microscopic traffic simulator, VISSIM, was used to simulate a freeway traffic stream and collect vehicle-maneuvering data. An external application program interface, the VISSIM COM interface, was used to implement the proposed VSL operations strategy. A surrogate safety assessment model was used to derive indirect safety measures to evaluate the effectiveness of the proposed methodology. Total conflicts in the proposed VSL algorithm were reduced in comparison with a system lacking VSL by 19.10% and 27.27% under moderately and severely foggy weather conditions, respectively. These outcomes are expected to be of great use in the development of more effective VSL systems to enhance freeway safety during adverse weather conditions.

Impact of Variable Speed Limit in a Connected Vehicle Environment on Truck Driver Behavior under Adverse Weather Conditions: Driving Simulator Study

“…Through a traditional safety analysis, the VSL system was found to be significant in reducing crashes. Choi and Oh proposed a proactive VSL strategy that employed visibility distance, safe stopping distances, and average speeds to reduce the potential of crashes under fog weather conditions ( 23 ). Simulation results indicated that with VSL control, traffic conflicts reduced by approximately 19 and 27% under moderate and severe fog weather conditions, respectively.…”

Preliminary Investigation of the Effectiveness of High-Visibility Crosswalks on Pedestrian Safety Using Crash Surrogates

“…The naturalistic driving study (NDS) data from SHRP 2 provide a unique opportunity to analyze such behavioral and environmental characteristics, before and after installation of the HVC (21). Because no pedestrianmotor vehicle crashes were observed in the Erie County, New York, SHRP 2 NDS test site, safety surrogates [i.e., speed, acceleration, throttle pedal actuation (TPA), and brake application] were used for the analysis (22)(23)(24)(25)(26)(27)(28)(29)(30)(31). The NDS data offer a good representation of the drivers' reactions to crosswalk striping and possibly to other safety countermeasures.…”

A Behavioral Model of Drivers’ Mean Speed Influenced by Weather Conditions, Road Geometry, and Driver Characteristics Using a Driving Simulator Study

“…Weather conditions' variables, particularly, heavy fog, negatively affected the mean speed and reduced it. In this regard, previous studies have examined the effect of foggy weather conditions on speed selection and have obtained similar results [10,[41][42][43][44]. However, contrary to the discussed results, Hamdar et al [45] concluded that fog density has little or no effect on drivers' speed selection behavior.…”