TRESIS: A transportation,land use and environmental strategy impact simulator for urban areas

The Institute of Transport Studies has developed a Transportation and Environment Strategy Impact Simulator (TRESIS) as a decision support system to assist planners to predict the impact of transport strategies and to make recommendations based on those predictions. A key focus of the simulator is the richness of policy instruments such as new public transport, new toll roads, congestion pricing, gas guzzler taxes, changing residential densities, introducing designated bus lanes, implementing fare changes, altering parking policy, introducing more flexible work practices, and the introduction of more fuel efficient vehicles. The appropriateness of mixtures of policy instruments is gauged in terms of a series of performance indicators such as impacts on greenhouse gas emissions, accessibility, equity, air quality and household consumer surplus. In this paper we introduce TRESIS to the research community, focussing on the structure of the system and the diversity of applications. Applications are presented to illustrate the diversity and richness of TRESIS as a policy advisory tool.     

Physically Realisable Feedback Controls for a Fully Active Preview Suspension Applied to a Half-Car Model

An optimal preview type active suspension with feedback control based on easily measured relative displacements, velocities and accelerations is proposed. Measurements relative to the road, except by the preview sensor, are not required and the front and rear spring rates are quite arbitrary. Also, state estimators or observers are unnecessary and as a practical alternative the body accelerometers may be replaced by load cells. The effects of preview on the performance, for a theoretical step type road input and an analogous random road input, are described. The definition of the optimum preview function, and its consequent effects on performance, receives attention and an example is given.     

Rail policy in Britain — What next?

The 1974 Railways Act set British Rail (BR) the rather vague objective of providing a passenger service broadly comparable with that then existing within a given level of support. For the first few years under the Act, BR succeeded in operating within the financial constraints imposed, but only by considerable increases in charges and by negotiating wage settlements which implied declining real wages. From 1978 on, rising labour costs and reduction in traffic led to a rapidly developing crisis in BR's financial position.The position of each section of BR's business is discussed briefly. It is shown that the designation of some sectors as being purely commercial is inappropriate, since this means that benefits to users and to the community at large are ignored in decision-making. Similarly, the direction to maintain social passenger services at a given level means that finance and investment are concentrated unduly on preservation of the existing pattern of service, rather than on providing value for money. In both sectors, the likelihood is that in general fares are too high and services too frequent.At an operational level, the criterion of maximising the (weighted) volume of traffic carried is advocated as a practical way of choosing between alternative fare and service-level packages. More broadly based strategic studies would be needed to decide on the weights to be adopted, the level of finance to be made available, and the overall strategy.     

Optimal Control of a Vehicle Suspension Incorporating the Time Delay between Front and Rear Wheel Inputs

An optimal control law for a vehicle suspension is developed using a discrete linear quadratic regulator framework. The time delay between the disturbance due to the road at the front and rear wheels is incorporated into the model, and it is shown that the optimal control law requires information gathered at the front wheels. A comparison is made between the optimal control law and a suboptimal one which does not incorporate front wheel road information.     

An Active Suspension with Optimal Linear State Feedback

In this paper modern optimal control theory is applied to the design of an active suspension system for a motor vehicle. The road profile is assumed to be continuous and random with a power spectral density (P.S.D.) which varies inversely with the square of the frequency. The quadratic integral type performance index employed is a weighted sum of the integral squares of body acceleration, dynamic tyre deflection and relative body-to-axle displacement. A solution is obtained for the infinite time case which is both computationally and physically realizable as an active suspension in which the only continuous measurements required are the body absolute velocity and the body displacement relative to the road. The performance is compared with that of a conventional type passive suspension and found to be significantly better in practically all respects.     

Investigation of soot formation in Diesel-GTL fuel blends under quiescent conditions

In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O₂ concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixing-controlled combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O₂ concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O₂ concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the formation of soot and NOx within a wide range of diesel engine loads.     

Possibilistic fuel cycle assessment of retrofit technologies for two stroke powered tricycles

Two stroke powered tricycles are a major source of air pollution in the Philippines. A fuelcycle assessment of the liquefied petroleum gas (LPG) and direct injection retrofit technologies for these vehicles is conducted. The results when compared with carbureted two and four strokes units indicate that retrofitting the units to direct injection provides lower fossil energy depletion, global warming, human toxicity and photochemical ozone formation impact potentials compared to LPG fueled carbureted two stroke tricycles while the latter exhibits lower acidification and nutrification impact values. The direct injection retrofitted units show a lower aggregated impact score and dominance over four stroke units. The conversion to LPG revealed minimal environmental benefits compared to the gasoline run units.     

Towed-Diver Surveys,a Method for Mesoscale Spatial Assessment of Benthic Reef Habitat: A Case Study at Midway Atoll in the Hawaiian Archipelago

An integrated method for benthic habitat assessment is described, in which divers maneuver boards equipped with digital video, temperature, and depth recorders while being towed behind a small boat. The tow path is concurrently recorded by a GPS receiver, and a layback model is applied to more accurately map the data. Percent cover of salient benthic categories is quantified by whole-image analysis of still frames sampled at 30-s intervals. The results of 15 towed-diver surveys at Midway Atoll in the Hawaiian Archipelago during a mass coral bleaching event are presented to exemplify the method and are compared to results derived from conventional methods. Towed-diver surveys bridge a gap between large-scale mapping efforts using satellite data and small-scale, roving diver assessments, providing a mesoscale spatial assessment of reef habitats. The spatial coverage of towed-diver surveys provides comprehensive data to managers concerning the extent, intensity, differential taxonomic response, and bathymetric correlates of bleaching.