speed
The current average driving speed in this direction. When the speed limit is close to 90, it is smooth. When it drops below 40, it usually means that the road ahead has started to be blocked.
means of transportation
Snow Tunnel Turtle King
Snow Mountain Tunnel real-time traffic condition signboard
How to read the Kanban board
Going south and going north are counted separately. Three numbers can determine whether to set off now and which road to cut before entering the tunnel.
queue length
Estimated array length (km). This number reflects the traffic jam earlier than the vehicle speed - the vehicle speed has not dropped yet, but the queue is already getting longer.
Suggested lanes
Based on the traffic flow on both sides, it is determined whether to go left or right. Lane changes are prohibited in the tunnel, so decide before entering the tunnel.
Basic information of Xueshan Tunnel
- full length
- 12.94 km
- speed limit
- 90 km/h (interval speed)
- Opening hours
- 24 hours
- driveway
- Two lanes in one direction, no lane changes allowed
- large car
- Drive in the outside (right) lane
- Smooth ride
- about 9 minutes
FAQ
What is the speed limit in the Snow Mountain Tunnel? Is there a speed test?
The speed limit is 90 kilometers per hour and there are
Why can’t I change lanes in a snow tunnel?
The space between lanes in the tunnel is
Is it faster to take the left or right lane in a snow tunnel?
There is no fixed answer, it depends on the current flow of traffic. Large vehicles are required to drive in the outside (right) lane, so there are often large vehicles on the outside and the speed is lower; but in traffic jams, the inside may also be slower. The upper signboard will directly give suggestions based on real-time vehicle speed and traffic flow status.
What is the total length of the Snow Mountain Tunnel? Approximately how long will it take?
full length
When are traffic jams most likely to occur in snow tunnels?
Consecutive holidays and weekends
How are these numbers calculated?
Speed and lane recommendations come from computer vision analysis of highway CCTV images, not manual reporting or simply reposting official data. Below is the entire process.
Current status:看板數值為展示用範例資料；即時分析管線正在整合中，尚未上線。
- 中央分隔線——左右車道由它分開
- 通過計數線——車輛跨過就計一次
- 追蹤框與車輛編號——同一台車跨影格的身分
Actual output of the analysis program (China 5 North 25K+335)
Why not just use the "pass rate" to decide?
因為 流量 ＝ 密度 × 速度，所以「通過率低」有兩種完全相反的意思：
Open and smooth - there are few cars, so the passing rate is naturally low (want to leave)
It’s so crowded that I can’t pass – there are too many cars but I can’t move (I want to avoid it)
單看通過率分不出來，所以改以車量與車速判斷。
Vehicle detection: YOLOv10
Frame the cars, motorcycles, buses and trucks in the picture frame by frame. The resolution of highway CCTV is only 352×240, and cars in the distance often have less than 20 pixels. Therefore, the detection threshold must be lowered, and subsequent geometric checks can be used to filter out misjudgments.
多目标追踪：ByteTrack
Merely framing a vehicle cannot calculate the speed - you must know where the "same car" is in the front and rear frames. The tracker is responsible for assigning a fixed ID to each vehicle so that the displacement is meaningful.
逆透视：像素换算成公尺
单一镜头没有深度资讯。 Assuming that the road surface is a plane, the displacement on the screen can be restored to the actual distance on the road surface by using the vanishing point where the lane lines intersect and the standard lane width of the national highway.
车道分流：中央分隔线
Taking the central double white solid line in the tunnel as the boundary, the vehicle falls on whichever side of the line belongs to which lane. The speed and volume of vehicles are counted in the two lanes respectively.
车速估计：中位数回归
Speed is the slope of time versus distance. The detection frame will jitter at low resolution, so take the median of the slopes of all sampling points instead of the least square - the median will not be pulled away by a single jump point.
建议车道：车量优先，车速否决
No pass rate judgment is required. Because flow rate is equal to density multiplied by speed, "low passing rate" may mean that it is empty and smooth, or it may be that it is too crowded to pass. Instead, it will be based on the average number of vehicles in the lane. If the speed difference is too large, it will be directly rejected by the vehicle speed.
The vehicle speed is an estimate of the monocular camera, which will be affected by calibration errors. It is for reference only before traveling and is not equivalent to the official speed measurement data.
Other common tools
The source of road condition data is traffic information published by the highway authorities. The values are system estimates and are for reference only before traveling. Please refer to on-site signs and traffic control.