Distributed Traffic Control Systems … · Any distributed solution must be highly tolerant of...

Distributed Traffic Control

Systems

Addressing the safety and availability challenges

Keith Manston© Siemens PLC 2019

Unrestricted © Siemens Mobility 2019

Keith Manston

Typical traditional cabling

What is meant by a distributed traffic control system

Plus+ Resilience by Design

Traditional traffic control systems use

many cables to connect street

furniture to the traffic controller

Cabling has many cores

➢ Large numbers of individual

connections

➢ Significant cable identing and testing

required during commissioning


Keith Manston

Picture of 16 core cable



Traditional traffic control systems use

many cables to connect street

furniture to the traffic controller

Cabling has many cores

➢ Large numbers of individual

connections

➢ Significant cable identing and testing

required during commissioning


Keith Manston



A distributed system such as Plus+

uses intelligence spread throughout

the intersection to significantly reduce

individual cable connections

A distributed system

SL

SL

SL

Traditional style signal head with

added intelligence

Traditional style nearside and

wait indicators

with added intelligence


Keith Manston







Plus+ allows street cabling to be arranged

in a different topographies to best suit the

intersection including:

➢ Arms

➢ Rings


SL

SL

SL


Keith Manston



Plus+ allows street cabling to be arranged

in a different topographies to best suit the

intersection including:

➢ Arms

➢ Rings

➢ Stars


SL

SL

SL






Keith Manston







Ideally system cables should be

non-specialist and commonly used

➢ Plus+ uses widely available standard

loop feeder cable


Keith Manston







Ideally system cables should be

non-specialist and commonly used

➢ Plus+ uses widely available standard

loop feeder cable

Picture of 4 against a 16 core cable


Keith Manston

Simple signal equipment

with voltage dependent

dimming doesn’t work when

multiple signals use the

same cable!

Some lessons learnt and experiences so far


Any distributed solution must

be highly tolerant of faults if

required operational up-time is

to be achieved

Developing a valid safety

case for a Distributed Traffic

Control solution is tricky and

very time consuming!

To avoid errors and minimise

wasted time, configuring distributed

items of on-street equipment must

be made easy and fool proof

The use of only

one type of standard

cable, with standardised

connections really does

make installation

easier To maximise civil cost savings,

sites ideally need to be designed

to take full advantage of minimalist

cable arrangements possible

With a system such as Plus+

It is really useful if the basic

controller configuration

process is familiar to users

and field staff Keeping the cabinet a

standard size is essential to

allow already installed

infrastructure to be re-used

Detailed modelling

has shown that the maximum

benefit of a distributed system

occurs when (nearly) all

cabling is eliminated


Keith Manston

But some of the biggest challenges are safety related!


How to ensure conflict & correspondence

performance is maintained

How to avoid avoiding partial dimming of

signals due to cable volt drops

How to maintain electrical safety

How to ensure distributed intelligence does

not reduce intersection availability


Keith Manston

❖ Make each signal node fail safe in its own right,

so it cannot illuminate a signal incorrectly, even

under fault conditions

➢Two processor safety and validation, with

independent means to extinguish node signals in

the event of a fault

❖ Use proprietary secure and authenticated

communications

❖ Use secret ‘monitor validation’ processes to

continually test system response to potential

errors

❖ Use robust and simple (for the installer)

processes to ensure individual signal nodes

are correctly allocated to phases











Keith Manston



❖ Eliminate the dependence on signal voltage to

determine when signals should dim

(Critical if multiple signals are to be

successfully powered from single cable)

➢Design signal nodes to illuminate signals at the

correct level across a wide range of supply

voltage at the node

➢Set required dimming level centrally as part of

the secure communications messaging to the

nodes

❖ Does offer opportunities for selectable

dimming levels (site to site) as once was the

case with incandescent signals









Keith Manston

❖ Deliver a fully ELV system only

➢Reinforces the need to ensure that signal

dimming is not voltage dependent

❖ Continue to ensue that provision is made to

allow all on-street infrastructure (poles,

pedestrian units etc) to be properly earthed

➢Typically via street cable armouring

❖ Continue to ensure that individual passively

safe poles can be electrically isolated in the

event they are struck

➢But for maximum availably ensure that where

possible the overall system is able to be

maintained in operation











Keith Manston



❖ Make each signal node fail safe in its own right,

so it cannot illuminate a signal incorrectly, even

under fault conditions

➢Allows failure of the node to be tolerated and the

rest of the intersection to continue to function

❖ Provide potential for a cabling architecture that

is tolerant of faults ( i.e. A ring topography)

❖ Provide a fault tolerant power supply system

with redundancy

❖ Enable replacement of key system components

(nodes, power supplies etc) whilst the

intersection remains operational

➢Make components ‘hot swappable’ where

possible









Keith Manston

So why do it – what are the benefits?

Health & Safety

Environmental

Installation Maintenance

Socioeconomic

Lighter cables

Less time

on site

Electrical Safety

(If ELV)

Less copper

Less civils

raw

materials

Faster

Less noisy work

Less disruption

Easier off site

prebuild

Less civils

Fewer cables

Less TM

Better availability

Better

diagnostics

Easier module

replacement

Cable

fault tolerance

More detailed

site inventory

Better Internal

self

checking

Less pollutionBetter value

for money



Keith Manston

How much cable can really be saved with a Plus+ system


Detailed modelling and first real site designs has shown that the maximum

benefit of a distributed system occurs when (nearly) all cabling is eliminated

➢ Up to 50% of cable cores at many poles

may not directly be used for RAG signals

❖ Pushbuttons, above ground detectors,

audibles, tactile units, regulatory signs

➢ Detector loop feeder cable can also account

for more than 50% of cables on some sites

It is essential therefore that these are all able

to be connected to the signal controller

without the use of additional cable cores


Keith Manston

How much cable can really be saved with a Plus+ system

Note:

Reductions shown are for material only and do not include additional benefits such as reduced

ducting or improvements derived from reduced effort required to pull cables, terminate or test

them.

This site includes passively safe poles, requiring those poles

to be individually wired back to the controller (hence the lower

than expected reduction in overall cable used).

However Plus+ eliminates the use of separate disconnect

system, removing the need for extra cabinets and equipment

etc and lowering costs


Conventional construction length (m)

Core

volume (cc) Conventional construction length (m)

Core

volume (cc) Conventional construction length (m)

Core

volume (cc)

20 core armoured 582 11,640 20 core armoured 4767 95,340 20 core armoured 4512 90,240

1 pair loop feeder 179 895 16 core armoured 3612 57,792 16 core armoured 317 5,072

2 pair loop feeder 428 4,280 1 pair loop feeder 2151 10,755

2 pair loop feeder 6476 64,760

Total 1189 16815 Total 8379 153132 Total 13456 170827

Plus+ construction length (m)

Core

volume (cc) Plus+ construction length (m)

Core

volume (cc) Plus+ construction length (m)

Core

volume (cc)

Plus+ cable 332 3,320 Plus+ cable 2170 21,700 Plus+ cable 5148 51,480

1 pair loop feeder 75 375 1 pair loop feeder 1103 5,515

2 pair loop feeder 55 550 2 pair loop feeder 2030 20,300

Total 462 4245 Total 2170 21700 Total 8281 77295

length (m)

Core

volume (cc) length (m)

Core

volume (cc) length (m)

Core

volume (cc)

61% 75% 74% 86% 38% 55%

Small 9 pole intersectionMedium sized 27 pole intersection with stub poles

and WiMagLarge 39 pole intersection with passively safe poles

Reduction Reduction Reduction


Keith Manston

What about savings in ducting etc?



Keith Manston



24/2

16/1

24/2

16/1

24/2

16/1

24/2

16/1

6/2

6/2

2/1

2/1

6/2

30/4

76/9

16/146/5

64/7

94/11182/20

(3 x 100mm Duct)

(1 x 50mm Duct)

This traditional system requires

minimum of 184 active cores in 21

individual steel wire armoured cables at

controller.

in practice many unused cores will also

be present at the controller which must

be terminated

Traditional system cabling


Keith Manston



8/2

8/2

8/2

8/2

8/2

1/4

8/2

6/2

2/1

2/1

4/1

1/4

4/1

4/1

4/14/1

4/1

4/18/2

Plus+ system requires just 8 active

cores in 2 individual steel wire

armoured cables at controller.

Makes the use of surface ducts or

simple slit cutting practical in this case,

where subsurface conditions make the

use of traditional ducting difficult

Plus+ system cabling

8/2

(1 x 60mm Surface Duct)


Keith Manston


By appropriately designing the architecture,

components and tools used in the Plus+

Distributed Traffic Control system, the complex

challenges posed by such systems have been

be met,

ensuring delivered intersections are as

efficient as possible to install and offer

the highest level of availability

throughout their design life

Distributed Traffic Control Systems … · Any distributed solution must be highly tolerant of...

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