TRANSYT is a software package developed in the UK

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 by the Transport Research Laboratory

Transport Research Laboratory

TRL is a British transport consultancy and research organisation based at Wokingham Berkshire with approximately 500 staff. TRL is owned by the Transport Research Foundation , which is overseen by 80 sector members from the transport industry. TRL also own small UK regional offices situated in...

. TRANSYT is the acronym for TRAffic Network StudY Tool.
It is used to assess and optimise the performance of networks of road junctions by assigning costs to vehicle stops and delays. This allows modelling of everything from individual junctions to 200 node networks, including unsignalled, partially signal-controlled or fully signal-controlled roundabouts

Roundabout

A roundabout is the name for a road junction in which traffic moves in one direction around a central island. The word dates from the early 20th century. Roundabouts are common in many countries around the world...

.

(Brief) History

Investigations carried out in the UK into possible improvements in traffic control of urban
networks in the 1960’s resulted in the development of TRANSYT/1 in 1967 by the Transport
Research Laboratory (TRL). Two trials of TRANSYT were carried out – one in Glasgow and
another smaller one in West London. The full-scale Glasgow trials were carried out with the
cooperation of the City Council in Glasgow. TRANSYT signal timings went ‘live’ in May 1967.
TRANSYT was shown to reduce the average journey times through the network of signals in
Glasgow by about 16 per cent. A similar reduction was recorded in the other smaller trial in
London. Because of TRANSYT’s international appropriateness TRANSYT is now one of the most
widely used signal timing programs in the world.


TRANSYT has continued to be developed by TRL ever since its first release.

Summary of Capabilities

Modelling of existing conditions and future conditions

Modelling of mixed signalled and unsignalled networks

Evaluation of time-varying traffic conditions

singal timing optimisation using a choice of three optimisers

Offset and split optimisation

phase and stage sequence optimisation

modelling of indirect traffic control effects

traffic steam-by traffic stream (lane-by-lane) analysis

Account taken of platoon dispersion and blocking-back effects

Modeling of flared junctions, storage in front of stopline and other complex junctions

Flexibility to model novel designs due to TRANSYT's building-block nature

Choice of units and driving-side

Data Requirements

Data input in Transyt involves:

• dividing roads and lanes into either links with shared signals and shared traffic movements; or using TRANSYT 14's ability to specify lanes and traffic streams;

• further dividing flows from different sources within a single section of roadspace using either shared links or letting the inherent ability of traffic streams to do this for you, in order to maintain the traffic arrival platoons.

• assigning a saturation flow to each link (or lane), indicating the maximum flow of traffic over the stop line during the green time;

• entering the signal timings that apply to each link (or traffic stream).

Results

Output includes:

For each link or traffic stream:

• a performance index (indicating the cost of the stoppages and delays on that link)
• the maximum capacity
• the degree of saturation
• the average maximum 'back of queue' length during the cycle
• the average queue length at the end of red
• practical reserve capacity (PRC)
• uniform, random and oversaturated delay
• animated uniform queues
• wasted green time
• WebTag-based fuel consumption
• various graphical outputs including time-distance diagrams and cyclic flow graphs

For the network overall:

• Performance Index (indicating the cost of the stoppages and delays within the network)
• total distance travelled
• mean journey speed
• fuel consumption

TRANSYT can also optimise signal timings over the network to find the combination with the lowest Performance Index. It does this using a choice of techniques - a hill-climb algorithm hill climb

Hill climbing

In computer science, hill climbing is a mathematical optimization technique which belongs to the family of local search. It is an iterative algorithm that starts with an arbitrary solution to a problem, then attempts to find a better solution by incrementally changing a single element of the solution...

, a shot-gun hill-climb (which takes longer but is likely to lead to better results) and Simulated Annealing

Simulated annealing

Simulated annealing is a generic probabilistic metaheuristic for the global optimization problem of locating a good approximation to the global optimum of a given function in a large search space. It is often used when the search space is discrete...

. The hill-climb algorithm looks for the lowest performance index and holds the signal timings that give the lowest performance index, only updating the timings if a more efficient set of timings has been found.

Current Release

TRANSYT 14's cababilties have been extensively extended to cover the modelling of wholly unsignalled junctions (Roundabouts, T-junctions, etc.) within signalised networks. TRANSYT 14 also includes the ability to model blocking back effects and platoon dispersion effects within the same network, which is particularly useful for the modelling and evaluation of all types of signalised roundabout, and any other network that contains a mix of long stretches of road, and short stretches of road that are prone to blocking back. This is performed using a combination of a Cell Transmission Model (CTM) and a Platoon Dispersion Model (PDM).

Summary of new features:

Modelling:

Blocking back and platoon dispersion modelled in the same network

Traffic Stream and Lane network representation

Mutual opposition modelling

RR67saturation flow estimation per lane


Optimisation:

Alternative optimisers (Hill-climb, Shotgun-hillclimb and Simulated Anealing)

Sophisticated OSCADY

OSCADY

OSCADY is a software package developed in the UK by the Transport Research Laboratory. The more recent phase-based version of the software is developed by Transport Research Laboratory in collaboration with UCL...

-style stage and phase optimisation

Phase and stage minimums and maximums

Too high and too low degree of saturation penalties


Graphical Interface:

File comparison tool and PDF or Word format reports

New and enhanced graphs

Data File Library (Template) system with graphical preview screen

Easier manipulation of signal data

SCOOT and SCATS traffic flow import

auto-mirroring of files for drive-on-the-right


Junctions:

Fully unsignalised junction modelling

Priority junction objects calculate give-way coefficients from geometric data*

Modelling of indirect traffic control effects at give-ways

Incorporates TRL's latest ARCADY

Arcady

ARCADY is the acronym for . This software, produced by the Transport Research Laboratory , provides information on traffic flow including modelling capacity queues and delays at roundabouts...

 and PICADY equations

• Requires active ARCADY 7 and/or PICADY 5 licence
  

International Features:

Drive on the left and drive on the right capability

Automatic mirroring of template files and instant re-orientation of networks

Alternative phase/stage/signal-group terminology

Auto-generated phases/stages/signal-group ID's can be numbers or letters

Many rules-of-the-road can be catered for

External links

• Transport Research Laboratory

TRANSYT Product Page: http://www.trlsoftware.co.uk/products/detail.asp?aid=4&c=2&pid=66