TRAFFIC BEHAVIOR DURING HIGHWAY MAINTENANCE AND REHABILITATION

摘要

This study was conducted to explore traffic flow characteristics during highway restricted operational conditions due to maintenance and rehabilitation in Iran. This was an attempt to identify freeway basic section traffic behavior during full or partial lane closures due to existence of damaged pavement, short-term and long-term maintenance and rehabilitation activities. Traffic observation and data collection were conducted for two freeway sites and resulted in five different operational conditions. For the first site, traffic data reflected three operational conditions namely, normal three-lane operation, special three-lane operation with one pavement damaged lane and two-lane operation with one short-term lane closure, respectively. For the second site, traffic data reflected two operational conditions namely, normal three-lane operation and two-lane operation with one long-term lane closure, respectively. Using a video camera with a timer, the traffic behavior was taped during working days of April to June 1999. Twenty two hours and thirty minutes of videotape were reviewed and relevant traffic information was extracted from the display on the television screen. The study database consisted of five minutes speed, density and flow rates. Univariate analysis of the observed traffic characteristics showed a number of interesting results, specially confirming significant speed and flow reductions during roadway maintenance and rehabilitation. Several traffic models including speed-density relationships were studied. For the five operational conditions, using the developed models, key numerical values of traffic flow characteristics such as free flow and capacity flow speeds, capacity flow rates, capacity flow densities and jam densities were identified. While traffic behavior will vary depending on the exact nature of the pavement damages, maintenance work being done, the number and size pf equipment at the site, the exact location of equipment and crews with respect to moving lanes of traffic, the criteria and observations cited in this study reflect representative records for a developing country such as Iran. Although the study findings were based on a rather limited database, the same methodology can be applied to explore traffic behavior during maintenance and rehabilitation under different circumstances.