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Game for congestion

Traffic management

Snowballing computer power is opening up a whole new world of possibilities for the modern traffic engineer. Alan Sparks reports.

Cyber babe Lara Croft is out to save the planet again. Only this time she is taking on a new evil - the fearsome traffic jam.

Faster, cheaper and more powerful graphics cards, initially developed for the computer games market, are now being put into action in the world of traffic engineering. And faster, higher resolution model animations mean bigger, more accurate simulations, giving traffic engineers new weapons to fight traffic congestion.

Traffic engineers have always had the theory to tackle traffic, explains Edinburgh City Council chief traffic engineer Duncan Fraser. Now, finally, technology has caught up.

Previous modelling packages have relied on tabulated figures to show effects, while others have modelled blocks or platoons of vehicles. These assume average values and as all traffic engineers know, traffic is never average.

'Today's 3D animations help inform the public and officials of the effects of any transport plan, in a language everyone can understand - far more easy to digest than a set of numbers in tables, ' explains Fraser.

Localised events can result in larger flow disruption as the ripple spreads across the network.

Analysing and predicting such events is a crucial step, which the new technology is equipped to tackle.

These micro-simulation models can now introduce variables such as awareness and aggressiveness. Such detail has existed in research models for some time, but even these models would run slower than real time.

'Now models can run traffic simulation faster than real time with far improved graphical visualisation, ' says Fraser.

'But the greatest benefit of these models is their ability to assess the impact of change on the whole network, ' says Fraser.

'The model can show exactly where congestion occurs and how this might be avoided.'

One such package is Paramics, which has been developed by Scottish firm SIAS.

Other similar systems are the German developed VISSIM and the Spanish GETRAM. Each of these recommends graphics cards that are used in games such as Lara Croft's Tomb Raider.

'Our package is capable of simulating any junction under any condition. Today I can run a model on a standard PC that handles 15,000 vehicles - in real time, ' says SIAS principal software engineer, Pete Sykes.

'Paramics has two real end uses, ' says Sykes. 'Though primarily for engineering it can also have presentational purposes.'

Sykes refers to a relatively small roadwork scheme that generated over 100 public objections. A public meeting was organised and a Paramics model used to show existing traffic flows, traffic flows during the works, and afterwards.

Instead of lists of numbers, the public could see the effects of the works on 3D vehicles - reducing queuing while also increasing overall traffic flows, explains Sykes. As a result, all but three objections were dropped and the scheme went ahead unhindered.

But the application of microsimulation goes beyond models of jam-prone sections of highway. The real potential, explains Fraser, is in identifying parts of a town that are likely to face real problems in the near future, forewarning traffic planners and allowing action to be taken before the problems develop.

'A small increase in traffic could lead to a massive impact to the flow, ' says Fraser. By analysing existing roads it is possible to see where the extra flow can be accepted without causing congestion elsewhere.

The environment is also set to benefit from the advance of technology, with simulations able to model different flow characteristics, which each produce a different type of pollution.

As a rule traffic engineers will try to encourage steady state flow to keep pollution to a minimum. But the type of pollutant that causes most concern differs depending on the road conditions. Nitrogen dioxide is the main pollutant from traffic running at 30km/h, whereas particulate matter is the most prominent pollutant when traffic is at a standstill. So engineers must decide what flow type they need, Fraser explains.

'What we have been able to do in Edinburgh is to attack the problem of traffic congestion from a completely different angle, ' says Fraser.

'Instead of maximising flows to gain greatest environmental benefit, we have determined the environmental capacity of each road and worked backwards to find how this can be controlled via traffic behaviour.'

Urban roads tend to be more sensitive to pollution, with far slower dispersal rates. So if a jam is inevitable, detailed modelling allows the engineer to channel traffic towards open spaces.

'Previous modelling was just too simple, ' says Fraser. 'Now engineers can have more confidence that their schemes will work as planned with all eventualities analysed before it is up and running.'

But such a thorough model must surely take a long time to learn how to use. Not so, claims Sykes. 'If you can run a windows program you can quite easily run this, ' With many major cities in the UK developing new public transport schemes, such as trams and guided buses, understanding the impact of bus lanes and red routes on traffic flows is increasingly important. Micro-simulation tools such as Paramics claim to avoid roundabout imbalance and pointless markings, and help develop advance signalling patterns.

But in reality does it really make that much difference? 'In Edinburgh this new tool has enabled us to attempt ambitious environmentally conscious schemes with a greater degree of certainty, ' says Fraser.

'These dummy runs allow optimal solutions to be attained, as dropping the ball in a computer simulation is not such a problem. Log-jamming a whole city is, ' says Fraser. 'These models provide an excellent tool for engineers to train and develop their skills like never before.'

With user feedback this strong, the creators of Paramics could be forgiven for resting on their laurels. But Sykes has bold plans for the future.

'At the moment city council and traffic engineers are using Paramics as a tool to help with traffic management and predict likely effects, ' says Sykes. 'But in the future we could see Paramics actually managing the road network.'


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