Relationship of Lane Width to Saturation Flow Rate on Urban and Suburban Signalized Intersection Approaches

Abstract

An understanding of the relationship between lane width and traffic operations is important in making decisions about urban and suburban arterials. Numerous geometric elements, including lane width, affect the saturation flow rate at an intersection on an urban or suburban arterial. Several studies have been conducted to evaluate the relationship between lane width and saturation flow rate at intersections. This relationship is investigated on urban and suburban signalized intersection approaches by using field-study sites with the most ideal conditions possible. Research results indicate that saturation flow rate varies with lane width. Average saturation flow rate was in the range of 1,736 to 1,752 passenger cars (pc)/h/ln for 2.9-m (9.5-ft) lanes, 1,815 to 1,830 pc/h/ln for 3.3- to 3.6-m (11- to 12-ft) lanes, and 1,898 to 1,913 pc/h/ln for lane widths of 4.0 m (13 ft) or greater. These measured saturation flow rates are generally lower than those currently used in the Highway Capacity Manual (HCM). Furthermore, the percentage difference in saturation flow rate between sites with 2.9- and 3.6-m (9.5- and 12-ft) lanes was about half the value used in the HCM. Because data were limited to queue lengths between 8 and 11 vehicles, the research results do not directly address queue lengths longer than 11 vehicles.

An Analysis of the Interactions between Adjustment Factors of Saturation Flow Rates at Signalized Intersections

“…In order to improve the accuracy of capacity estimation, adjustment factors become the focus of research. The common adjustment factors include lane width, vehicle composition, and various shared lanes [20][21][22][23][24][25][26][27][28][29][30][31][32].…”

“…Based on the survey data, the relationship model of lane width and speed is developed. It is found that lane width is positively correlated with saturation flow rate [20][21][22]. Zegeer et al [20] studied the saturation flow rate at different scenarios in which the lane width of 2.6 to 4.7 m (8.5 to 15.5 ft).…”

“…The narrower lane widths demonstrated saturation flow rates from 2% to 5% lower than those in the baseline surveys, whereas the wider lane widths demonstrated saturation flow rates 5% higher. Potts et al [21] studied the relationship between lane width and saturation flow rate on approaches at signalized intersections located downtown and in suburban areas. It is found that saturation flow rate varies with lane width.…”

Increasing Signalized Intersection Capacity with Unconventional Use of Special Width Approach Lanes

“…Considering the special road geometric conditions, mixed traffic composition, and very limited space, many transportation researchers and practitioners have proposed to shrink the width of existing approach lanes and save space for addition of extra lanes while it may bring negative impact on saturation flow rate, travel speed, and operational safety (Potts et al., ; Rosey et al., ; Isebrands et al., ; Wood et al., ). As an important element in geometric design of street, the lane width has long been discussed.…”

Relationship of Lane Width to Speed for Urban Expressway: A Case Study in Shanghai

“…Studies on the lane width have been done for a long time, mostly investigating the effect of lane width on safety (2) and capacity (1,3), but fewer studies concern the effect on speed. As following, a comprehensive review of previous studies that dealt with the impact of lane width on speed will be presented from the aspects of highway/freeway.…”