26/10/2018

Subject:Freedom of Information request - Current traffic light system in Hong Kong (Case Ref: 2-4838813847)

Dear Sir/Madam,

Thank you for your email to the Transport Department dated 24/10/2018. Please note that 1823 of the Government helps the Transport Department receive public enquiries and complaints via its e-mail box "[Transport Department request email]", telephone hotline "2804 2600" and fax hotline "2804 2652".

We have referred your case to the Transport Department. You will be informed of the outcome as soon as possible.

If you have any enquiries, please contact us.

Best regards,
Viola Tong
Customer Service Officer
1823

Tel: 1823
Fax: 2760 1823
Email: [email address]

(For effective handling of your case, all our conversations may be recorded, irrespective of whether you dial in or we call you back.)

Dear Ms Tsang,

I refer to your email dated 24.10.2018 requesting for information on
traffic light system in Hong Kong.  Our reply to your request is as
follows.

1. How does the traffic signal system work in Hong Kong?

Area traffic control (ATC) in Hong Kong is basically the traffic signal
control system centralized and coordinated by means of computer system, on
an area-wide basis.  Put simply, the traffic signal controllers on street
are linked to the central computer at the Transport Department (TD)'s
control centres.  As such, signal settings can be optimized on an area
basis to reduce overall delay and reduced travel times.   Different
traffic conditions during different periods of a day can be catered for
with  pre-determined multi-plan operation. The time settings of traffic
signals on the streets can also be adjusted by manual intervention such as
modifying the existing signal timing plan or replacing it with a new plan,
in a remote manner. The ATC System can be used for the continuous
monitoring of the operation of the traffic signal equipment.  Fault
condition detected can also be reported to the control centre and fault
repairs can be carried out quickly.
   
2. As I know, there are detector loop underground to collect traffic data
to adjust traffic signal system. But how frequent the TD adjust the signal
with the data?

Loop detectors on the traffic lanes can help allocate signal time
automatically according to the actual traffic condition. This is a
vehicle-actuated mechanism, and is a continuous adjustment process.  On
the other hand, there is another kind of adjustment through manual process
which depends on professional judgment.  TD's manual adjustment of the
traffic signal does not rely on the detector loop, but rely on actual
observation including CCTV, site inspection and public reporting, etc.  

3. When is the last time TD adjust the time of traffic light?

Changing of signal time at a vehicle-actuated signal (detector loop mode)
is automatic and continuous. Pre-determined multi-plan setting will be
adjusted on a need basis.  In general signal setting is adjusted for
individual junction or a small group basis, rather than on an area basis.
 As there are about 1 800 signalised junctions covered under our ATC
systems, adjustments to individual junction often take place from time to
time.  

4. Can I have data which shows the duration of traffic signal system in
different region?

Every junction has its unique signal time allocation to cope with its
particular traffic condition.  A longer cycle time usually produces a
higher traffic capacity, but will increase the waiting time for the
non-green directions.  A balance is needed to be made for setting the
cycle time depending on the traffic condition.  In general, if the traffic
condition is busier, the longer the cycle time will be.  However, if you
are interested at a particular junction, please let us know the specific
locations for our processing.

5. Is there any difference on the operation of traffic lights between peak
hour and non-peak hour?

Yes, generally cycle time at peak hours is longer than those at non-peak
hours in order to cope with the heavier traffic flows.

6. As I know, during peak hour, the traffic light time is fixed. Whether
the time is the same in different region, for example, traffic light in
TST and CWB at peak hour.

There is no direct relationship between the traffic signal time setting
and the district located.  It is set individually based on the particular
traffic conditions at that junction.   In general, the more traffic in a
particular direction, more green time would be allocated.

7. Is there any real time adjustment on traffic light?

There is mechanical real time adjustment under vehicle-actuated mode.  The
mentioned loop detector belongs to this kind.  Also, traffic signal plans
and settings can be adjusted real-time in our control centre via remote
control.

Should you have further enquiry, please contact our Ms Sophia Chu at 2829
5359.

Thank you.

Yours sincerely,

Miss Dorothy Chim
for Commissioner for Transport

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