Investigation of Traffic Safety Effects of Speed Limit Increases in Main Arterials

Türe Kibar, Funda
Tüydeş Yaman, Hediye
Setting safe speed limits requires consideration of different factors (operating speeds, road hierarchy, etc.), especially in urban corridors. With a legislative change, speed limits were increased from 50 km/hr by 32 km/hr on some urban arterials in Turkey, effect of which is examined for Ankara urban arterials in this study. Shifts in traffic accident hotspots, which were determined using Nearest Neighborhood Hierarchical (NNH) Clustering in Geographical Information System (GIS) environment, are quantified using three different indices as Hit Rate (HR), Predictive Accuracy Index (PAI) and Recapture Rate Index (RRI). The 3-year before and after cases included 1533 accidents and 1687 accidents, respectively. NNH with minimum accident number, n min =5, and maximum distance, d max = 100 m, produced 88 clusters covering 900 accidents (HR=58.71%) for the before case, while it detected 93 clusters with 926 accidents (HR= 54.89%) for after case. While higher d max values increased cluster numbers slightly, d max =500 m produced fewer clusters in both cases, as more accident data were associated in a cluster with high distance tolerance. Though there was a slight decrease in fatality statistics after the increase, a slight increase in number of hotspots and accidents suggests that i) the operating speeds were already high before, ii) the traffic safety along the corridors did not improve much, though it may ease enforcement of the corridors, iii) it increased the dispersion of accident locations decreasing HR values (not desired, as it may endanger effectiveness of traffic safety countermeasures).
13th International Congress on Advances in Civil Engineering, ACE2018 (12 - 14 Eylül 2018)


Realistic Simulation of IEEE 802.11p Channel in Mobile Vehicle to Vehicle Communication
Islam, Tarikul; Hu, Yongchang; Onur, Ertan; Boltjes, Bert; De Jongh, J. F. C. M. (2013-04-18)
Intelligent Transportation Systems (ITS) is becoming an important paradigm, because of its ability to enhance safety and to mitigate congestion on road traffic scenarios. Realizing the fact that data collection scheme from in-situ test beds for large number of vehicles is always expensive and time consuming, before being employed in large scale, such safety critical system should be tested narrowing down the gap between real circumstances and analytical models in a simulation platform. It is evident that un...
Evaluation of pedestrian safety around bus stops using geographic information systems
Yüksekol, İrem; Tüydeş Yaman, Hediye; Department of Civil Engineering (2012)
Pedestrians are the most vulnerable road users in terms of traffic safety. Public transit users mostly have a pedestrian trip before and/or after the transit one. Thus, pedestrian activity is produced at transit stops naturally. The main focus of this study is pedestrian safety problems around transit stops, more specifically bus stops. The proposed methodology first includes Geographic Information Systems (GIS) analyses of the pedestrian safety along the study corridors and around bus stops on them; this e...
GIS-based evaluation of the speed limit increase on urban arterial traffic safety in Ankara
Kibar, Funda Ture; Tüydeş Yaman, Hediye (Springer Science and Business Media LLC, 2020-06-14)
Setting safe speed limit is very critical and complex phenomenon, which has to be decided based on the road hierarchy that categorizes roads according to their functions and capacities, and poses certain restrictions in the design process. However, this is challenging in urban regions of developing countries, where rapid city growth forces high-speed intercity roads to serve as urban arterials, along which traditional 50 km/h limit is not practically possible. To lower the speed variation (and provide mobil...
Influence of traffic enforcement on the attitudes and behavior of drivers
Stanojevic, Predrag; Jovanovic, Dragan; Lajunen, Timo (2013-03-28)
Traditionally, traffic enforcement has been an important means of improving traffic safety. Many studies have provided evidence of connections between the level of police enforcement and both driving behavior and the number of traffic accidents. In Northern Kosovo, there has been little, if any, traffic enforcement during the last 13 years. This situation has created a very rare research opportunity - it is now possible to directly study the influence of traffic enforcement on the attitudes and behavior of ...
Evaluation of approach leg capacities at a signalized urban roundabout
Saltık, Ege Cem; Tüydeş Yaman, Hediye; Department of Civil Engineering (2018)
Intersections are vital components of road networks, which provide ability to change directions serving many conflicting movements. When the traffic volumes are high, intersection control is necessary via either signalization or by design such as roundabouts. However, the even latter is mostly signalized in Turkey due to improper design aspects and driver behavior issues. When signalized, approach capacity at an intersection/roundabout is governed by the saturation flow rate, , as well as the allocated effe...
Citation Formats
F. Türe Kibar and H. Tüydeş Yaman, “Investigation of Traffic Safety Effects of Speed Limit Increases in Main Arterials,” presented at the 13th International Congress on Advances in Civil Engineering, ACE2018 (12 - 14 Eylül 2018), Çeşme, İzmir, Türkiye, 2018, Accessed: 00, 2021. [Online]. Available: