Urban streets are essential parts in cities and their development can enhance various aspects of economic life and social activities. Al-Najaf city is one of the Iraqi developing cities that has been suffering from traffic congestion at various sections of its street network. The reasons, locations and intensities of these congestions are important to be regularly diagnosed for two key reasons: first, in order to choose the right traffic engineering solutions and second to adequately prioritize the funding required for planning and implementing the traffic management programs for these congested sections. This paper attempts to evaluate the performance of the main urban streets located within the southern part of Al-Najaf city street network during evening peak hours. The methodology includes collecting field data and conducting traffic surveys such as traffic volume, travel time and free flow speed surveys. The evaluating approaches illustrated in the U.S Highway Capacity Manual are adopted as a tool for assessing the operational performance for the selected urban streets. The results reveal that there are several segments that operate at their capacity (LOS E) or even under congested flow condition (LOS F). The analysis also shows that whereas some segments are with good LOS using volume-capacity ratio (v/c) criterion, they are actually with low LOS based on field observations or when using travel time as a performance measure. This indicates the inadequacy of using v/c ratio alone in evaluating urban streets because part of the congestion at such streets is due to side friction operational delays rather than over traffic demand.

城市街道是城市的重要组成部分，其发展可以促进经济生活和社会活动的各个方面。纳杰夫市是伊拉克发展中城市之一，其街道网络的各个部分一直受到交通拥堵的困扰。这些拥堵的原因、位置和强度对于定期诊断很重要，主要有两个原因：第一，为了选择正确的交通工程解决方案，第二，充分优先考虑为这些拥堵规划和实施交通管理计划所需的资金。部分。本文试图评估位于纳杰夫城市街道网络南部的主要城市街道在晚高峰时段的表现。该方法包括收集现场数据和进行交通调查，如交通量、旅行时间和自由流动速度调查。美国公路通行能力手册中说明的评估方法被用作评估选定城市街道运营绩效的工具。结果表明，有几个段以其容量 (LOS E) 或什至在拥塞流量条件 (LOS F) 下运行。分析还表明，虽然某些路段使用容积容量比 (v/c) 标准具有良好的服务水平，但根据实地观察或使用旅行时间作为性能衡量标准，它们实际上具有较低的服务水平。