Following is a question by the Hon Michael Tien and a written reply by the Secretary for Transport and Logistics, Ms Mable Chan, in the Legislative Council today (October 8):

Question:

     It is learnt that since the installation of a traffic signal system at Pok Oi Roundabout in Yuen Long on February 9 this year, members of the public and motorists generally consider that the system has effectively eased traffic flow and significantly improved traffic conditions at the roundabout. In this connection, will the Government inform this Council:

(1) of the comparisons of the following traffic data at Pok Oi Roundabout before and after the installation of the traffic signal system:
(i) the average traffic queue length (in metres) at each of the southbound and northbound entrances during peak hours (7am to 10am and 5pm to 8pm);
(ii) the time period during which the longest traffic queue occurred and its duration;
(iii) the average time taken for vehicles to pass through the roundabout; and
(iv) changes in the number of traffic incidents (set out by nature of the incidents); and

(2) whether it has plans to, after obtaining data confirming that traffic signal systems can effectively improve traffic flow and safety at roundabouts, conduct a comprehensive study on installing a real-time adaptive traffic signal system at every roundabout in Hong Kong, with a view to using artificial intelligence and big data to monitor traffic flow and adjust signals in real time; if so, of the details; if not, the reasons for that?

Reply:

President,

     The Pok Oi Roundabout is a major hub in Yuen Long and a key route for vehicles travelling to and from Yuen Long Town in the Northwest New Territories. Heavy traffic flows are observed at Pok Oi Roundabout during morning and evening peak hours, resulting in increased travelling time. The Government has been monitoring the traffic situation there and has implemented several road improvement works in phases. After consulting the Transport Department (TD), my response to the question raised by the Hon Michael Tien is as follows:

(1) Traffic improvement measures at Pok Oi Roundabout in Yuen Long, which include the installation of traffic signal controls and the widening of the exit to Au Tau, were implemented on February 9, 2025. The traffic signal controls effectively balanced the flow of vehicles at various entrances of the roundabout, allowing vehicles to enter in an orderly manner. The widening of the exit to Au Tau provided additional road space, streamlining the traffic flow there. As the daily traffic pattern and variations at the Pok Oi Roundabout are relatively stable, the current traffic signal time plan set for different time periods has effectively streamlined the traffic flow, thereby significantly shortening the traffic queues and queuing time to enter the roundabout, and enhancing its operational efficiency. The traffic data before and after the implementation of the aforementioned traffic improvement measures is provided at Annex.

(2) Roundabout is a common design of road intersection in Hong Kong. In general, roundabouts can self-regulate the vehicular flow, enabling smooth passage of vehicles from various directions under varying traffic volumes. The TD continuously monitors the traffic conditions and implements feasible improvement measures as needed, such as adjusting traffic lane designs, optimising road markings and signage, to maintain smooth operation of roundabouts and ensure road safety.

     Under certain traffic conditions—particularly when exceptionally heavy volumes enter the roundabout from one or more directions—the roundabout's self-regulating capacity may become overwhelmed. In these instances, installation of traffic signals at appropriate locations of roundabout can control the approaching traffic, allow vehicles from different directions to enter the roundabout in an orderly manner and enhance its operational efficiency (such as Pok Oi Roundabout in Yuen Long).

     In addition to the traffic flow characteristics in roundabouts aforementioned, the TD takes into account a range of factors when considering the installation of traffic signals at a roundabout. These include the necessity for traffic signals, the size of roundabout, road layout, geographical constraints, and driver behavior.

     Regarding the enquiry about installing a Real-time Adaptive Traffic Signal System (RTATSS) at roundabouts, RTATSS uses sensors placed at junctions and employs AI to analyse traffic patterns in real time—across various directions and time periods. It calculates and optimises the allocation of green time to improve flow for both vehicles and pedestrians, effectively balancing the needs of all road users. RTATSS implemented under pilot project undertaken by the TD are currently operating smoothly, with data showing an approximate 5 per cent to 10 per cent reduction in average delay for vehicles passing through the junctions, thereby enhancing the operational efficiency of junctions. The TD is planning to implement the RTATSS at approximately 50 suitable isolated signalised junctions across the territory with the first batch scheduled for commissioning in 2026. The TD is also arranging pilot installations at other linked signalised junctions with relatively heavy traffic flow to test relevant technologies from other places (including the Mainland). This will contribute to the formulation of plans for the wider adoption of RTATSS at other suitable junctions.

     Regarding the installation of RTATSS at signalised roundabouts, the technical complexity is greater compared to conventional signalised junctions because the system has to simultaneously detect and process traffic circulating within the roundabout as well as traffic waiting to enter the roundabout from each approach lane. The TD will review the feasibility of extending RTATSS to signalised roundabouts after accumulating more experience from its application at conventional signalised junctions.

Ends/Wednesday, October 8, 2025
Issued at HKT 12:00

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