4Intelligent transport systems requirements#
4.1Introduction#
Refer also to Section 1. ITS are information and communication technologies applied to road infrastructure and vehicles to improve road safety and efficiency as well as reduce impact on the environment of transportation systems. They have proven to be an innovative alternative to traditional measures for addressing transportation problems and needs. ITS applications vary, from simple traffic control and traveller information systems to the rapidly-evolving automatic incident detection applications and vehicle to infrastructure cooperative systems.
ITS systems include:
- vehicle detection sites (VDS)
- vehicle counter / classifiers
- closed circuit television (CCTV) systems / Web cameras
- road weather monitoring
- Help phone systems
- variable message signs (VMS)
- changeable message signs (CMS) systems
- road condition information signs (RCIS)
- variable speed limit / lane use signs (VSL / LUMS)
- travel time signs (TTS)
- ramp metering systems
- weigh-in-motion (WIM) systems, and
- automatic number plate recognition (ANPR) systems.
All of these systems require power supplies and, because of the electronic components of many of the systems, appropriate surge and lightning protection.
4.2Design philosophy#
ITS design must take into account road geometry, landscape design, drainage systems, road structures, other road furniture such as static signs, lighting, services such as electricity and public utility plant and supplies. Likewise, these services must consider ITS requirements. This will allow addressing conflicts that may arise regarding ITS equipment space allowances, conduit routes and sighting distances with other road services. Site and maintenance access are critical aspects of all ITS designs.
Electrical designs must consider the most effective means of providing safe and reliable ITS systems. ITS systems will generally be single phase using the two-wire MEN system. In larger three-phase power installations, the four-wire MEN system must be used. An earth electrode and MEN link will be required at the switchboard and field cabinet.
Where three-phase circuits are used, the load must be balanced across the phases as evenly as possible.
4.3Electrical design requirements#
4.3.1Design voltage and frequency#
The design voltage is 230 V ac.
The design frequency is 50 Hz.
4.3.2Design current and power factor#
Manufacturers’ data, where available, must be used for the selected equipment. Where this is not available, current measurement, load assessment or specified protection size should be used.
4.3.3Design spare capacity#
The consumers’ mains, submains and sub-circuit design must optimise both the available EFLI and voltage drop. Unless otherwise specified in the project-specific requirements, a single-phase 10 A design current should be allowed for each field cabinet.
4.3.4Maximum demand#
The maximum demand for each sub-circuit and socket outlet will be the connected load.
The running current load on any circuit must not exceed 80% of the circuit protection rating.
The maximum connected load for switchboards must not exceed 63 A three-phase.
4.3.5Discrimination#
For ITS systems, it is essential that any electrical fault is cleared by the protection closest to the fault, while leaving other parts of the installation operational.
The electricity entity fuse at the point of supply is expected to be 80 A.
The field cabinet protection fuse is 20 A, unless otherwise specified in the project-specific requirements. This may be located within the cabinet or within a switchboard, particularly when a number of cabinets are supplied from the one switchboard.
The surge filter fuse for the field cabinet is rated at 20 A, or to suit the protection fuse size.
Sub-circuit fuses are rated at 10 A.
With this configuration, discrimination is achieved for both overload and short-circuit faults for high rupture capacity fuses complying with AS 60269.
4.3.6Disconnect time#
The maximum disconnect time for fuses protecting cables (including consumers’ mains cables) directly connected to metal enclosed electrical equipment (that is, top mounted switchboards, metered switchboards, ITS switchboards, field cabinets, post / gantry mounted equipment, and the like) is 400 ms.
The maximum disconnect time for fuses protecting cables (including consumers’ mains cables) directly connected to non-metal, insulated enclosed electrical equipment (that is, pillar mounted switchboards, and the like) is 5 s.
4.3.7Cable operating temperature#
The cable operating temperature of 75°C should be used in all cable electrical calculations.
4.3.8Voltage drop#
Total voltage drop in ITS circuits must allow for consumers’ mains, submains and sub-circuit voltage drops, the sum of which must be no greater than 5%, using the circuit maximum demands.
The voltage drop at any point in an extra low voltage circuit must not exceed 10% of the nominal voltage when all live conductors are carrying the circuit operating current.
In addition, voltage drop at any ITS equipment must not be more than that required for safe and reliable operation of the equipment.
Refer also to Section 7.
4.3.9Earth fault loop impedance#
EFLI calculations must be carried out to demonstrate that the design is compliant for the worst-case protection and cable length for each of consumers’ mains, submains and final sub-circuits.
The assumed ratio of 20% external and 80% internal impedance has been found not to be valid for Transport and Main Roads’ field installations and must not be used.
Obtain the supply transformer and distribution cable parameters from the Electricity Entity and include these in the calculations. Where exact network data are not available or measurement of supply characteristics is not practicable, the designer must make an assessment of the relevant parameters and clearly document these in the design calculations.
Refer also to Section 7.
4.3.10Point of supply#
Points of supply must be agreed with the Electricity Entity within a reasonable time frame to allow the Electricity Entity to carry out any necessary network modifications without delay to the project.
ITS circuits may be connected to road lighting switchboards on separate fuses upstream of the lighting contactor.
ITS equipment specific for an intersection controlled by a traffic signal controller may be connected to the controller; however, protection sizes / types for the ITS equipment must be selected to ensure that total discrimination is achieved with the controller circuits.
4.3.11Electrical connection of intelligent transport systems equipment#
ITS equipment is generally connected to the power supply located within the field cabinet.
One double, general purpose socket outlet is permitted within the field cabinet and this must be RCD protected.
Individual socket outlets should be used for specific equipment, unless the equipment is designed to be hardwired.
RCDs are not required on socket outlets (other than the double, general purpose socket outlet), provided the requirements of AS/NZS 3000 Clause 2.6.3.2.1 Exception 5 are met.
No spare socket outlets are to be available for future connection. Where future additional equipment is required, a new socket outlet is to be installed by a registered electrician and the increased load advised to the Electricity Entity.
Each copper circuit – both power and communications entering or leaving the field cabinet – must have appropriate surge protection.
Refer to Section 5.
4.3.12Intelligent transport systems equipment mounted on structures#
ITS equipment mounted on structures must have an earth conductor connected to the equipment and to the earth at its circuit origin. The earth cross-sectional area must be the same as the active conductor size.
4.3.13Connecting intelligent transport systems equipment to traffic signal controllers#
The following equipment may be connected to a traffic signal controller provided the minimum conditions as detailed are met:
| System | Connection | Comment |
|---|---|---|
| Radar detectors, pedestrian detectors, call wait detectors, and so on | Connect to 240 V supply red core of 36 c multicore cable | Install a 2 A fast blow fuse between the supply and the detector if not individually fused The detector signal is brought back to the controller on a spare white core |
| Red light cameras | E1 / E2 / E3 | Refer SD1703 |
| CCTV cameras mounted on signal posts | Connect to 240 V supply red core of 36 c multicore cable or external supply | Install a 2 A fast blow fuse between the supply and the camera Fuse and camera supply must be installed in separate weatherproof enclosure. |
| CCTV cameras mounted external to intersection | Generally connect to own point of supply | Alternatively, connect to separate MCB in traffic controller, subject to RPEQ review for specific cases |
| ITS equipment installed within the controller | Connect to RCD SO circuit | The RCD-protected terminals of the controller SO must be used for connection of additional socket outlets |
| ITS equipment mounted on signal posts | Connect to 240 V supply red core or external supply | Install a 2 A fast blow fuse between the supply and the equipment Fuse and equipment supply must be installed in separate weatherproof enclosure |
| ITS equipment mounted external to intersection | Generally connect to own point of supply | Connection to separate mcb in traffic controller, subject to RPEQ review for specific cases; for example, where communications cabinet is located adjacent to controller |
| Flashing wigwags | Connect the flasher unit to a dummy signal group in the controller | Use ETG 6471 or AWA 2G65843 flasher units |
4.4Electrical components#
4.4.1General#
Refer to SD1699 Traffic signals / Road lighting / ITS – Parts list, which provides details of standard electrical equipment items. Items approved by ITS and Electrical must be used.
4.4.2Switchboards#
ITS switchboards are:
| ITS switchboards are: | |
|---|---|
| Top mounted | Refer SD1690 |
| Plinth mounted | Refer SD1689 |
Refer also MRTS226.
Where an upstream Link switchboard is required – for example, on long cable runs where there is a need to reduce the size of the circuit protection for EFLI considerations – a link switchboard may be used:
| used: | |
|---|---|
| Single-phase | Refer SD1687 |
| Three-phase | Refer SD1688 |
Only where the Electricity Entity network characteristics are such that the 80 A fuse will not activate within 400 ms to clear an active-to-earth fault at the switchboard may a pillar mounted switchboard be used; however, this should be used only when other cost-effective design options are not available.
| Unmetered | |
| Pillar mounted | Refer SD1430 and SD1676 |
4.4.3Main switch#
The main switch must be a labelled, single-phase switch disconnector, lockable in the open position, with minimum utilisation category AC 22 A, minimum 20 A capacity, and complying with AS/NZS IEC 60947.3.
4.4.4Fuse switches and ruselinks#
Electrical protection for ITS circuits should be provided by single-phase fuse switches complying with AS/NZS IEC 60947.3, with minimum utilisation category AC 22 A, complete with HRC fuselinks complying with AS 60269 and utilisation category gG. Standard fuselinks are:
| Fuselink | Application |
|---|---|
| 40 A | Top mounted, metered or pillar mounted switchboard |
| 20 A | Field cabinet main protection |
| 10 A | Field cabinet sub-circuits |
4.4.5Residual current devices#
An RCD must be used on general purpose socket outlets and lighting circuits.
Where fixed equipment is direct connected or where a socket outlet is installed for the connection of specific equipment, an RCD is not required, provided all the requirements of AS/NZS 3000 Clause 2.6.3.2.1 have been met.
Refer Section 5.
4.4.6Earth and neutral bars#
Earth and neutral bars must be suitable for 25 mm² cables.
4.4.7Cables#
As far as practicable, use the standard power cable sizes in SD1699 Traffic signals / Road lighting / ITS – Parts list. Where the design requires otherwise, use manufacturers’ standard cable appropriate to the installation requirements.
Cables up to and including 6 mm² must comply with AS/NZS 5000.2.
Cables 16 mm² and larger must comply with AS/NZS 5000.1.
Direct buried cables, SDI cables, neutral screened cables, steel wire armoured cables and the like must not be used for ITS circuits.
Electrical cables must be installed in an electrical conduit and pit system.
Where large size cables are used, particularly on long runs, the cables may be joined to a suitably sized tail:
- within the equipment, and
- using a suitable waterproof joining method in the pit.
4.4.8Conduits and pits#
Conduit for both electrical and communications systems must be heavy duty UPVC or high density polyethylene (HDPE) complying with AS/NZS 61386.
The following table details the minimum conduit and pit requirement for ITS installations:
| Conduits for ITS | Requirements |
|---|---|
| Telstra point of presence to ITS communications pit | 1 x 100 C |
| ITS communications pit to field cabinet | 2 x 100 C |
| Point of supply to ITS electrical pit | 1 x 80 E |
| ITS electrical pit to field cabinet | 2 x 100 E |
| Field cabinet to earth pit | 1 x 20 E |
| Detection loop to loop pit | 1 x 32 E |
| Loop pit to ITS electrical pit | 1 x 50 E |
| ITS communications pit to ITS communications pit | 1 x 100 C (min) |
| ITS electrical pit to ITS electrical pit | 1 x 100 E (min) |
| ITS field equipment to ITS pits | 1 x 100 E, 1 x 100 C |
| Under road crossings | 2 x 100 E, 2 x 100 C |
| In concrete barrier | 1 x 100 E, 1 x 100 C |
| Pits for ITS | Requirements |
|---|---|
| ITS electrical pit | circular |
| ITS communications pit | circular |
| ITS earth pit | P3 |
| Road crossing electrical pit | P8, circular |
| Road crossing communications pit | P8, circular |
| Detection loop pit | P3 |
| Intermediate pit | circular |
| Exit of concrete barrier | circular |
| Single field cabinet electrical pit | P8,circular |
| Single field cabinet communications pit | P8,circular |
| Double field cabinet electrical pit | P8,circular |
| Double field cabinet communications pit | P8,circular |
Where there are installations with large numbers of cables, the conduit numbers may need to be increased so that the maximum conduit fill for any conduit does not exceed 40%.
4.5Design documentation#
For each design, submit to Transport and Main Roads a copy of the electrical design calculations, and an Electrical Design Certificate completed and certified by a practising profession electrical engineer currently registered with the Queensland Board of Professional Engineers (RPEQ).
The calculation sheet must clearly show all design inputs and calculation results, along with compliance checks, so that the design can be easily verified. Include the following:
- project name / description
- consumers’ mains / submains cable size, length and load
- sub-circuit cable size, length and load
- total voltage drop.
- Electricity Entity network data used, including consumers’ mains fuse and disconnect time, measured external EFLI, or assessment data used (indicated as assessed, and)
- calculated total EFLI at the end of each low voltage circuit including external EFLI.
4.6Schedule of intelligent transport systems design information#
The following information must be completed by Transport and Main Roads and included in ITS tender documentation for electrical design:
| Item | Typical requirements |
|---|---|
| Field cabinet design current | 10 A |
| Preferred pit size | P7, P8, circular |
| Approved equipment to be used | (state) |
| External equipment to be connected to field cabinet | (state) |
| Spare electrical design capacity | (state) |
| STREAMS connection | Yes / No |
| Preferred communications connection | DSL / Fibre Microwave |
| Location of nearest communications point of presence | Departmental fibre splice pit / Telstra pit |