Modelling car trip generations for UK residential developments using data from TRICS

Abstract

This paper models trip generation for a cross-section of residential developments around the UK. Consistent with recent literature, the empirical model tests whether trip making patterns for residential developments are independent of car ownership and finds that trip generation is dependent upon car ownership socio-economic factors and site-specific characteristics, in particular land-zone type (e.g. town centre, out of town, etc.). However, public transport services are not found to have a significant relationship with trip generation; consequently, a policy implication of the results is that increasing bus services to residential developments is not associated with a reduction in generated trips.     

The biogeochemical cycling of methane in Ria de Vigo, NW Spain: Sediment processing and sea–air exchange

Methane (CH₄) concentrations were measured in the water column, in sediment porewaters, and in atmospheric air, in the Ría de Vigo, NW Spain, during both the onset (April 2003) and at the end of (September 2004) seasonal upwelling. In addition, CH₄ concentration and stable isotopic signatures (δ¹³CH₄) were measured in porewaters, and sediment methanogenesis and aerobic oxidation of CH₄ were determined in sediment incubations. Surface water column CH₄ (2 m depth) was in the range 3–180 nmol l^− 1 (110–8500% saturation) and followed a generally landward increase but with localised maxima in both the inner and middle Ría. These maxima were consistent with CH₄ inputs from underlying porewaters in which CH₄ concentrations were up to 3 orders of magnitude higher (maximum 350 μmol l^− 1). Surface water CH₄ concentrations were approximately three times higher in September than in April, consistent with a significant benthic CH₄ flux driven by enhanced sediment methanogenesis following the summer productivity maximum. CH₄ and δ¹³CH₄ in sediment porewaters and in incubated sediment slurries (20 °C) revealed significant sediment CH₄ oxidation, with an apparent isotopic fractionation factor (r_c) of  1.004. Using turbulent diffusion models of air–sea exchange we estimate an annual emission of atmospheric CH₄ from the Ría de Vigo of 18–44 × 10⁶ g (1.1–2.7 × 10⁶ mol). This estimate is approximately 1–2 orders of magnitude lower than a previous estimate based on a bubble transport model.     

Hatchcoverless container ships: productivity gains from a new technology

The hatchcoveless container ship is an innovative design which improves cargo handling productivity. The paper develops a methodology for measuring the gains. To illustrate the impact of faster port times on voyage profitability a voyage cost analysis is used to show its operational advantages. An investment analysis demonstrates the value which will accrue to the company over the life of the vessel.     

Assessing transportation user benefits with maximum trip lengths

Maximum time lengths of urban trips can be used to calculate major user benefits of transportation improvements. These benefits include those associated with reduced cost of travel, those associated with travel to additional destinations, and those associated with improved quality of destinations. Maximum trip lengths can be measured using techniques of psychological scaling.     

Measuring unobserved prices using the structural time-series model: The case of cycling

This study presents a means of determining a historic (generalised cost based) price index for cycling in the UK for the period 1949–2006 using annual demand data. By specifying demand as a function of generalised price and income and then applying a structural time-series model to elucidate the unobserved component of prices (while controlling for observed income levels), it is illustrated that the role of prices in influencing demand is non-trivial. Over the sample period price responses generally influence demand for cycling to a greater extent than income effects.     

Updating predictive accident models of modern rural single carriageway A-roads

Abstract

Reliable predictive accident models (PAMs) are essential to design and maintain safe road networks, and yet the models most commonly used in the UK were derived using data collected 20 to 30 years ago. Given that the national personal injury accident total fell by some 30% in the last 25 years, while road traffic increased by over 60%, significant errors in scheme appraisal and evaluation based on the models currently in use seem inevitable. In this paper, the temporal transferability of PAMs for modern rural single carriageway A-roads is investigated, and their predictive performance is evaluated against a recent data set. Despite the age of these models, the PAMs for predicting the total accidents provide a remarkably good fit to recent data and these are more accurate than models where accidents are disaggregated by type. The performance of the models can be improved by calibrating them against recent data.     

Decoupling of Road Freight Transport and Economic Growth Trends in the UK: An Exploratory Analysis

Abstract

Between 1997 and 2004, gross domestic product increased in real terms in the UK by one‐fifth, while the volume of road freight movement remained stable. This suggests that the long‐awaited decoupling of economic and freight transport growth has begun, possibly leading to a new era of sustainable logistics. This paper reviews previous research on the decoupling issue and recent trends in gross domestic product/freight tonne‐km elasticities in Europe and the USA. It then examines 12 possible causes of the observed decoupling in the UK using published statistics from a wide range of British and European sources. This analysis indicates that around two‐thirds of the decoupling is due to three factors whose impact can be quantified: the increased penetration of the British road haulage market by foreign operators, a decline in road transport’s share of the freight market, and real increases in road freight rates. Several other factors, most notably the relative growth of the service sector, the diminishing rate of centralization, and the off‐shoring of manufacturing, appear to be having a significant effect, though this finding cannot be measured on the basis of available statistics. The paper concludes that, while the decoupling is in the right direction from a public policy standpoint, the net environmental benefits are likely to be quite modest.