Operational Effectiveness of Passing Zones Depending on Length and Traffic Volume

Abstract

Most studies on two-lane highway operations have focused on the percentage of following vehicles or the adjustment of the Highway Capacity Manual (HCM) procedure to local data. The HCM proposes the length of no-passing zones as a model parameter; however, the distribution and characteristics of passing zones are not addressed. In fact, only a few studies on the expected number of passes in a passing zone have been carried out. This research presents an analysis of the effectiveness of passing zones in terms of their length and traffic volume. Data were collected from four passing zones on a rural highway in Spain. The two-way traffic volumes ranged from 100 to 900 vehicles per hour (vph), and the passing zone lengths ranged from 265 to 1,270 m. More than 1,600 passing maneuvers were recorded. The operational effectiveness of the passing zones was obtained from the passing frequency and the passing rate. The results indicated that the longer the passing zone, the higher the passing frequency; however, the results stabilized with lengths above 1,100 m. Balanced flows with two-way traffic volumes between 600 and 700 vph optimized the number of passes. Nevertheless, the increase in the passing frequency with the traffic volume was lower than with the increase in following vehicles. The results were validated with data from another 12 passing zones. Finally, HCM adjustments based on the percentage of no-passing zones did not reliably represent the effectiveness of passing zones. Therefore, the effectiveness of every passing zone should be considered, and adjustment factors should be modified to maximize the passing opportunities for traffic volumes between 600 and 700 vph.

Development of a new microscopic passing maneuver model for two-lane rural roads

“…The dynamic methodology used as instrumented vehicle one light vehicle (414 passes in 18 h) and one truck (46 passes in 8 h). Static observations characterized passing frequency, measured in passes per hour (Moreno et al, 2013). Hourly traffic volumes, as well as percent of followers entering the observed passing zones were also registered.…”

Design Criteria for Minimum Passing Zone Lengths

“…On one hand, authors did not validate TAM with this study, assuming TAM initial calibration based on 1970's data (9). Moreover, the number of passing maneuvers was very little, compared to other field studies (10)(11)(12)(13). The difference on traffic flows, directional split, passing zone length and maybe local driver behavior resulted in dispersion on the number of passes.…”

“…The macroscopic data were obtained from four passing zones ranging 265 to 1,270 m long, and hourly traffic volumes of 140 vph and 335 vph (10,25). Macroscopic data of traffic volume, percent followers and number of passing maneuvers characterized the operation of single passing zones.…”

“…The passing zone lengths were generally higher than 500 m, so the conclusions may not be representative for short passing zones. Only two studies included short passing zones (1,10) There have been previous research focused on the development of passing models for traffic microsimulation. However, their level of detail, their validation or the fields of application are not homogeneous.…”

When Do Drivers Abort an Overtaking Maneuver on Two-Lane Rural Roads?

“…These studies adopted a behavioural approach to understand drivers' gap-acceptance decisions and the factors that influence these decisions [14,15,18,19]. Other studies focused on: classification of overtaking maneuvers [13], evaluation of the overtaking sight distance [20,21], evaluation of the risk associated with various overtaking sight distance lengths [22], estimation of overtaking duration and distance [16,23,24], overtaking intentions [25,26], impact of drivers' age and gender [27,28], evaluation of overtaking rates, operational effectiveness of overtaking zones, and capacities [17, 29,30], and the design of overtaking assistance systems [9]. However, none of the previous studies have focused on understanding the conditions that lead drivers to abort overtaking maneuvers, and the characteristics of these aborted maneuvers.…”