Highway Bureau, MOTCHighway Bureau, MOTC

Jenshui Tunnel is located between Hejen and Dachingshui with a length of 2.9 km, and it is not a long tunnel and is the last part of Suhua Highway Improvement Project. Considering the factors of geology, environmentally sensitive area, and the matching alignment between new and old Provincial Highway No. 9, the tunnel is designed as single hole with dual lane in order to reduce the area of excavation and decrease the impact toward environmentally sensitive area. The section between Hejen and Dachingshui is not over three kilometers in length, and the layout of lanes is one fast line and one slow lane in both directions to separate different types of vehicles. Therefore, motorcycles are allowed in Jenshui Tunnel. For road safety, the speed limit on this section is 50 km/ per hour.

The total length of Suhua Highway Improvement Project is 38.8 kilometers. Although it is a general provincial highway, there are 8 tunnels, with a length 24.5 kilometers in total, and it accounts for 63% of the whole highway. Among them, there are 4 tunnels with a length of 3 kilometers or more, and it accounts for 53% of the whole highway. Guanyin Tunnel and Gufeng Tunnel are connecting to each other, and the total length of the two tunnels is 12.6 kilometers. Compared with general provincial highway, Suhua Highway Improvement Project consist various tunnels. On top of that, it opens to large truck, making the types of vehicles using the highway a lot more complicated than Xueshan Tunnel on National Freeway No. 5. Considering there is only one lane, the most important topic when Suhua Highway Improvement Project is underway is the road safety in tunnels.
With the condition of only one lane on both traffic direction on Suhua Highway Improvement Project, as well as the consideration of ventilation, temperature, Suhua corridor accident prevention, vitalization and development of the existing settlement on Suhua Highway, and transportation flow of passenger and cargo vehicles, it is planned at the design stage that the types of vehicles can use Suhua Highway Improvement Project are small vehicles, large passenger vehicles, large trucks (including semi-trailers). In terms of motorcycles, due to the ratio of large truck in the total vehicle types on Suhua corridor (around 15% on March 9th, 2020 (Monday)) as well as the light and road environment in the closed environment of tunnel over 3 kilometers are not as good as that on general road, we take into account the high risk of motorcycles mixed in the traffic flow with large vehicles on the single lane in the long tunnel and motorcycles are relatively vulnerable in protection measures among carriers. Therefore, the conclusion is that no motorcycles shall be allowed on Suhua Highway Improvement Project, except for the section of “Hejen to Dachingshui”.

Due to different driving environments in different countries, not all long tunnels allow motorcycles to ride through. In addition, the ratios for different vehicle type are also different in the long tunnels in other countries, as well as the design of the tunnel is usually two holes with dual lane. Therefore, the control strategy of vehicle type going through the long tunnel will not be exactly the same. As the result, we have to evaluate the traffic condition in Taiwan when planning and controlling the type of vehicle using Suhua Highway improvement Project in order to maintain the road safety for users.

The main purpose of “Suhua Highway Improvement Project” is to solve the long-term problems of poor road alignment, easy to be snapped by landslides, and higher accident rate on three sections of Suhua Highway, including Su’ao to Dong’ao, Nan’ao to Heping, and Heping to Dachingshui. In consideration of the maintenance of environment and ecology as well as the reduction of impact on the local area after opening it to the public, the purpose of Suhua Highway Improvement Project is not for mass transportation. That is why it is designed with only one lane to maintain existing road capacity.
Due to the rural location, we also consider the demand of rescue in the shortest time if there is any emergency in the tunnel. Thus, emergency rescue paths are established in Dong’ao Tunnel, Guanyin Tunnel, Gufeng Tunnel, and Zhongren Tunnel in order to allow disaster-rescue vehicles, like police cars, fire engines, and ambulances, access to the tunnel as soon as possible.