"We have just acheived in six weeks what we failed to acheive in the previous eight years"" The impact on the councillors at Transportation Committee was profound, and was demonstrated by the limited number of questions they asked, because they could see before thir own eyes the direct impact of traffic management changes within the city centre."These unsolicited comments come from local authority chief officers following their first encounters with SIAS's Paramics Microsimulation service. What is it about, and how can anything provided for so little be any good ? This paper attempts to unravel the mystery. Because of the public funding requirement, Transport Planning is not unusual in having to grapple with the conflicts of demand, pragmatism and dogmatism. Although they may share the same degree of social acceptability, politicians and transport planning professionals make a particularly bad mix, the formers' modus operandi being centred on good communication, while the latter’s relates to anything but. Local authority transport planners have traditionally faced an uphill struggle communicating their best solutions, because they are too often the messenger of an obscured message. This may come from an appointed external consultant, a whipping boy who often gets the upper hand by way of obfuscation. This is derived from an output delivery system rooted in Byzantine methodologies developed to sell computers to town halls in the 1960s, but which has little to do with solutions to traffic congestion in the 21st century. Traffic engineers may have been first with computer models, but sadly those models are still in use, as fossilised rocket science now turned into a black art. Politicians somewhat distanced from the technical action should question the validity of the advice they receive. This comes from chief officers in equally dependent positions, the chain of marginal understanding disappearing out of the local authority domain to where all manner of trickery may be deployed by consultants. The outline plan may come from the politician, but what comes back has to be sufficiently robust to survive public scrutiny. Politicians cannot risk some fatal flaw lurking inside a mound of largely unintelligible paper. There is no suggestion here that we, politicians, local authority officers and consultants, are universally crooks and charlatans. We have all been victims of a process where integrity depends on validation criteria derived more from Highway Agency's interpretation of arithmetical expediency than any adherence to reality. This process is a function of the traffic model, a combination of computer software and data on traffic movements to describe traffic flow. A modern term refers to multi-modal models, although, in truth, there's no such thing. Politicians more than anyone else will understand this, that you can only pack as many people on the buses as your marketing budget can achieve. It has nothing whatever to do with a traffic model, multi-modal or otherwise. The reader may already be familiar with the traffic model as a potential source of salvation and grief. While politicians may be in the fortunate position of ultimately ignoring them altogether, they nevertheless form a useful procrastination function, without which we'd have to find some other objective process of expedient inaction. Traffic models are idealised representations which ignore illegally parked cars, bus stops, incidents, irate drivers, lollipop ladies, roadworks, bad weather, malfunctioning signals, and any other event likely to be encountered on a real journey. Traffic planners ignore these obvious features, and opt for a more obscure pipe flow analogy. This concept just about works in a wide context because strategic traffic models are intended to be no more than convenient repositories of data to be used in a broad manner, but the method does not translate to the congested urban network which most of us are concerned with. To a general public which takes sophisticated computer systems in the living room for granted, the approach to transport planning is very curious. Traffic models embody the notion that obvious problems do not exist, with the result that politicians and the general public have become sceptical of a process which exists only in the hope that something else must surely be along soon. Contemporary models are "deterministic", which means that if "A" happens, then "B" will occur. In reality, "B" sits within a fuzzy range, but traffic modellers have great difficulty assimilating this, and in presenting it in a manner which can be readily understood by those who have to take the decisions on behalf of those who remain to be convinced. A commonly held notion among transportation planners is that their models are "quite good", but there is a general recognition that their underlying demographic and economic data are anything but. The oldest dictum in the computer users handbook, that rubbish in equals rubbish out, is obscured by transportation models, because it is difficult to interpret what is coming out. Transportation planners seem to think the rule cannot apply to them, and rarely seek the evidence to deflect them. Some well-used big models are so awful as to be virtually worthless, but they continue to exist because they are deemed to be "validated" against dubious technical criteria. Almost all models are "wrong" in some crucial aspect, so how can decisions based on them be right? While embracing large commercial enterprises, local authorities face problems dealing with the large developers, whose individual transport impact assessments may summate to a hidden structural strategic change. Messrs Sainsbury, ASDA, and IKEA have their own agendas, and the local transport vision gets blurred. Very soon, we are led to believe, transportation budgets are to enjoy a significant boost, and if this is not to degenerate into chaos we all need to get a grip. By straightening the fundamental basis of local authority transportation planning, chief officers and their staff can stop firefighting and control their own technical destiny. The opening quotes to this paper suggest that it is possible to bring general clarity and understanding to the proceedings and enable an extraordinary efficiency to emerge. This clarity is now emerging across the UK and the rest of the world, by way of a transportation modelling system known as "S-Paramics". This directly models the components of traffic flow and congestion in a manner that is recognised by all by presenting the output as a graphical display of real-time traffic flow. This is not an animation of some other modelling system, but the modelling system itself. It's also interactive, so ideal for quick scenario testing and decision making in circumstances hitherto deemed impossible. S-Paramics cuts through the mathematical proxy misrepresentation of transportation models and their outputs, which take so long to interpret by simulating and presenting a recognisable real world. It represents individual components of traffic flow and congestion, and presents its output as a real-time visual display, for traffic management and road network design. In addition to the inclusion of detailed physical description of the transport infrastructure, such as road layout, bus services and transport interchanges, driver and vehicle behaviour are represented. Transportation Planners have been slow to recognise that such a simple concept can work. After all, traffic is chaotic and complex, so the tools for analysis must surely be complex. Traffic may be complex, but it is a complex order, physically constrained by the road network. Behind the apparent randomness of road traffic, there is order based on simple rules of car following, gap acceptance and vehicle kinematics. These produce complex behaviour over a wide area when traffic densities are high, and prone to chaotic processes which are sensitive to small disturbances. These can produce large `butterfly effects', such as the familiar shock wave phenomenon of congested motorways. In one recent study conducted by SIAS it was discovered that a twenty minute incident cleared at one point on a road network could generate a queue within a shock wave over an hour later at some 5km distance, an event which microsimulation systems can represent and evaluate. Such effects are ignored by non-microsimulation systems, but can be so severe as to dwarf the effects traditionally evaluated for scheme assessment. According to conventional traffic models, the two lane capacity of the A720 Edinburgh City Bypass is sufficient to cope with peak flows, but any driver will tell you that a queue is guaranteed. This is because of the three incidents each day, and two-lane stretches are now being widened, not to three lanes, but with a continuous hard shoulder. The benefit of this was demonstrated with S-Paramics microsimulation, visualising an effect which non-microsimulation systems cannot show. In short, where real effects take over, only S-Paramics can analyse and present these to a wide audience. It would be dangerous to assume entirely that "seeing is believing", but if the model looks wrong to anyone, then it probably is wrong. Traffic planners and engineers are thankfully conservative by nature, and have viewed microsimulation with suspicion, considering it a revolutionary approach with insufficient integrity. But, as they continue to struggle with systems designed to address issues of an earlier age, they may look towards their contemporaries in dozens of cities from Edinburgh to Buenos Aires and realise that there is another way. There is little to be suspicious about, because, with S-Paramics, what you see is what you get. If a microsimulation model doesn't look right, then it probably isn't, and vice versa. It is little more than applied common sense. S-Paramics puts the capability and power into the appropriate hands, and delivers the message to the people who need to know. It does not fool or fudge and can have a dramatic effect on timescales at all stages of design, decision and public consultation. My opening quotes suggest that others believe this to be true.
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Important handbooks available to SIAS clients and S-Paramics licence holders |
