Russo Brendan J, Savolainen Peter T, Gates Timothy J, Kay Jonathan J, Frazier Sterling
a Department of Civil Engineering, Construction Management, and Environmental Engineering , Northern Arizona University , Flagstaff , Arizona.
b Department of Civil, Construction and Environmental Engineering , Iowa State University , Ames , Iowa.
Traffic Inj Prev. 2017 Jul 4;18(5):521-527. doi: 10.1080/15389588.2016.1261123. Epub 2016 Nov 28.
Although a considerable amount of prior research has investigated the impacts of speed limits on traffic safety and operations, much of this research, and nearly all of the research related to differential speed limits, has been specific to limited access freeways. The unique safety and operational issues on highways without access control create difficulty relating the conclusions from prior freeway-related speed limit research to 2-lane highways, particularly research on differential limits due to passing limitations and subsequent queuing. Therefore, the objective of this study was to assess differences in driver speed selection with respect to the posted speed limit on rural 2-lane highways, with a particular emphasis on the differences between uniform and differential speed limits.
Data were collected from nearly 59,000 vehicles across 320 sites in Montana and 4 neighboring states. Differences in mean speeds, 85th percentile speeds, and the standard deviation in speeds for free-flowing vehicles were examined across these sites using ordinary least squares regression models.
Ultimately, the results of the analysis show that the mean speed, 85th percentile speed, and variability in travel speeds for free-flowing vehicles on 2-lane highways are generally lower at locations with uniform 65 mph speed limits, compared to locations with differential limits of 70 mph for cars and 60 mph for trucks.
In addition to posted speed limits, several site characteristics were shown to influence speed selection including shoulder widths, frequency of horizontal curves, percentage of the segment that included no passing zones, and hourly volumes. Differences in vehicle speed characteristics were also observed between states, indicating that speed selection may also be influenced by local factors, such as driver population or enforcement.
尽管之前已有大量研究探讨了限速对交通安全和运营的影响，但其中大部分研究，以及几乎所有与差别限速相关的研究，都仅限于无出入口控制的高速公路。无出入口控制的公路上独特的安全和运营问题，使得难以将之前与高速公路限速相关的研究结论应用于双车道公路，尤其是关于因超车限制和后续排队导致的差别限速的研究。因此，本研究的目的是评估农村双车道公路上驾驶员速度选择相对于公布限速的差异，特别强调统一限速和差别限速之间的差异。
从蒙大拿州及周边4个州的320个地点的近59000辆车辆收集数据。使用普通最小二乘回归模型，在这些地点考察自由流车辆的平均速度、第85百分位速度和速度标准差的差异。
最终，分析结果表明，与汽车限速70英里/小时、卡车限速60英里/小时的差别限速地点相比，双车道公路上统一限速65英里/小时地点的自由流车辆的平均速度、第85百分位速度和行驶速度变异性通常更低。
除公布的限速外，还发现有几个地点特征会影响速度选择，包括路肩宽度、水平曲线频率、无超车区路段的百分比和小时交通量。各州之间还观察到车辆速度特征的差异，表明速度选择也可能受到当地因素的影响，如驾驶员群体或执法情况。
