The latest transportation law in the United States continues to put emphasis on a performance management approach similar to the previous one. Since the transportation performance management rules were made in 2017, limited work has been done to understand the travel time reliability on the national highway system (NHS) and the factors influencing it. This study contributes to the literature by analyzing the characteristics of the unreliable segments of the NHS in 13 south eastern states. It was observed that there was a higher percentage of unreliable segments in the non-Interstate NHS (about 34%) than in the Interstate system (about 13% of segments were unreliable). Analyses of the unreliability of the Interstate and non-Interstate NHS were conducted separately to understand each of them better. To capture the influence of the attributes on the reliability of the NHS segments, multivariate binary logistic models were developed. The results from the models suggest that the reference traffic message channels (TMCs), which were characterized by being in urban areas with shorter length (≤0.25 mi) and ≤10% trucks in the traffic stream, generally have a higher chance of being unreliable than those that are not in the reference category. Interstate TMCs on bridges, tunnels, or causeways, and those with directional traffic volume greater than 30,000, have higher chances of being unreliable than the reference category. The chances of internal TMCs (between decision points) in the non-Interstate NHS being unreliable were about 14% higher than the mean chance of the reference TMCs.

美国最新的运输法继续将重点放在类似于以前的绩效管理方法上。自2017年制定运输绩效管理规则以来，为了解国家公路系统（NHS）的行驶时间可靠性及其影响因素所做的工作很少。本研究通过分析东南13个州的NHS不稳定部分的特征，为文献研究做出了贡献。观察到，非州际NHS中不可靠段的百分比（约34％）比州际系统中高（约13％的段不可靠）。分别对州际和非州际NHS的不可靠性进行了分析，以更好地理解它们。为了捕获属性对NHS段可靠性的影响，开发了多元二进制逻辑模型。模型的结果表明，参考交通消息通道（TMC）的特征是位于交通流中长度较短（≤0.25 mi），卡车≤10％的市区，通常具有较高的不可靠机会比那些不在参考类别中。桥梁，隧道或堤道上的州际TMC，以及定向流量大于30,000的州际TMC，与参考类别相比，不可靠的可能性更高。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。建立了多元二元逻辑模型。模型的结果表明，参考交通消息通道（TMC）的特征是位于交通流中长度较短（≤0.25 mi），卡车≤10％的市区，通常具有较高的不可靠机会比那些不在参考类别中。与参考类别相比，桥梁，隧道或堤道上的州际TMC，以及定向流量大于30,000的州际TMC，具有更高的不可靠机会。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。建立了多元二元逻辑模型。模型的结果表明，参考交通消息通道（TMC）的特征是位于交通流中长度较短（≤0.25 mi），卡车≤10％的市区，通常具有较高的不可靠机会比那些不在参考类别中。与参考类别相比，桥梁，隧道或堤道上的州际TMC，以及定向流量大于30,000的州际TMC，具有更高的不可靠机会。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。它们的特点是在交通流中长度较短（≤0.25英里）且卡车≤10％的城市地区，与那些不属于参考类别的卡车相比，其不可靠的机会通常更高。与参考类别相比，桥梁，隧道或堤道上的州际TMC，以及定向流量大于30,000的州际TMC，具有更高的不可靠机会。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。它们的特点是在交通流中长度较短（≤0.25英里）且卡车≤10％的城市地区，与那些不属于参考类别的卡车相比，其不可靠的机会通常更高。与参考类别相比，桥梁，隧道或堤道上的州际TMC，以及定向流量大于30,000的州际TMC，具有更高的不可靠机会。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。与参考类别相比，不可靠的可能性更高。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。与参考类别相比，不可靠的可能性更高。非州际NHS中内部TMC（决策点之间）不可靠的机会比参考TMC的平均机会高约14％。