# Estimation of Optimal Speed Limits for Urban Roads Using Traffic Information Big Data
## 2 Theory and Prior Studies
### Speed Limit Setting Criteria
#### 2.1.2 Overseas Criteria  
In Australia, the speed limit for urban arterial roads is 60 km/h in general. However, speed limits of 60 km/h or higher are not generally used in many OECD countries, and 50 km/h is widely used instead. The speed limit is generally 50 km for collector and local roads, and many OECD countries use a limit of 30-40 km/h [3]. The detailed speed limit by country is shown in Table 2.  
Most OECD/ITF [4] countries use 50 km/h as the default speed limit for passengers in cities. Low speed limits (typically 30 km/h) are applied to residential areas and near schools. The default speed limit of 60 km/h is applied in Poland, Chile, and South Korea.  
Japan [5] established speed regulation standards (12 standards) for general roads in 2009, considering the three factors of traffic accident risk, the existence of median, and pedestrian protection in urban areas based on the results of the \"Study on the direction of speed limit decision\" in 2009.  
The U.S. abolished the 55 mph maximum speed limit, which had been enforced by the federal government since 1974 (April 1995), and delegated authority to state governments so that they could define the speed limits for all roads (urban and regional) (TRB: Transportation Research Board, 1998) [6].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Classification** & **Maximum Speed** & **Minimum Speed** \\ \hline General road: 1 lane direction & 60 km/h & - \\ General road: more than 2 lane directions & 80 km/h & - \\ Expressway & 90 km/h & 30 km/h \\ Freeway: 1 lane direction & 80 km/h & 50 km/h \\ Freeway: more than 2 lane directions & 100 km/h & 50 km/h \\ Freeway: designated by metropolitan & 120 km/h & 50 km/h \\ \hline \hline \end{tabular}
\end{table}
Table 1: Current statutory maximum speed limits in South Korea.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Country** & \begin{tabular}{c} **Urban Arterial** \\ **(km/h)** \\ \end{tabular} & **Local and Collector** & **Country** & \begin{tabular}{c} **Urban Arterial** \\ **(km/h)** \\ \end{tabular} & **Local and Collector** \\ \hline USA & 48–88 & 40–56 & Mexico & 80 & 20–60 \\ \hline Australia & 60–70–80 & 50 & Netherlands & 50–70 & 50 \\ \hline Austria & 50 & 50, 40 (residential) & New Zealand & 50–80 & 50 \\ \hline Canada & 50–60 & 40–50 & Norway & 50 & 30–50 \\ \hline Czech Republic & 50–60 & 50 & Poland & 50 & 50 \\ \hline Denmark & 50 & 50 & Portugal & 50–90 & 50 \\ \hline Finland & 50 & 30–40–50 & Russia & 60 & 60 \\ \hline France & 50 & 30–50 & Sweden & 50–70 & 30–50 \\ \hline Germany & 50 & 50 & Switzerland & 50 & 50 \\ \hline Greece & 50–70–90 & \
\begin{tabular}{c} 40–50 (collector), \\ 30 (local) \\ \end{tabular} & United Kingdom & 48–64 & 32–48 \\ \hline Iceland & 50–60 &
\begin{tabular}{c} 50 (collector), \\ 30 (local) \\ \end{tabular} & South Korea & 60 (1 lane direction), 80 (more than 2 lane directions) \\ \hline Ireland & 50–80 & 50 & \\ \hline \hline \end{tabular}
\end{table}
Table 2: General speed limits in OECD countries.  
Sweden (WHO, 2008) [7] has set speed limits to prevent deaths and injuries based on the philosophy of 'Vision zero' since the 1960s and is benchmarked in Europe as a good example of speed limit establishment.  
The WHO (2013, 2015) [8; 9] reported that 97 out of 180 countries around the world have urban maximum speed limits equal to or lower than 50 km/h and emphasizes that more countries should introduce 50 km/h as the maximum speed based on its accident reduction effect. In these countries, higher speed limits are applied as an exception to some roads such as urban belt highways. The following Figure 2 shows the classification of the speed limit by country/area.