Rocco Zito

Integration of the global positioning system and geographical information systems for traffic congestion studies

Abstract The Transport Systems Centre (TSC) has developed an integrated Global Positioning System (GPS) – Geographical Information System (GIS) for collecting on-road traffic data from a probe vehicle. This system has been further integrated with the engine management system of a vehicle to provide time-tagged data on GPS position and speed, distance travelled, acceleration, fuel consumption, engine performance, and air pollutant emissions on a second-by-second basis. These data are handled within a GIS and can be processed and queried during the data collection (from a notebook PC in the vehicle) or saved to a file for later analysis. The database so generated provides a rich source of information for studies of travel times and delays, congestion levels, and energy and emissions. A case study application of the system is described focusing on studies of congestion levels on two parallel routes in a major arterial corridor in metropolitan Adelaide, South Australia. As part of these investigations, a discussion of the nature of traffic congestion is given. This provides both a general definition of traffic congestion and the discussion of a number of parametric measures of congestion. The computation of these parameters for the study corridor on the basis of data collected from the integrated GPS–GIS system is described. The GIS provides a database management platform for the integration, display, and analysis of the data collected from GPS and the in-vehicle instrumentation.

GLOBAL POSITIONING SYSTEMS IN THE TIME DOMAIN: HOW USEFUL A TOOL FOR INTELLIGENT VEHICLE-HIGHWAY SYSTEMS?

Abstract Much of the research and development work in intelligent vehicle-highway systems (IVHS) relies on the availability of methods for locating and monitoring vehicles (e.g. “probe vehicles”) in real time across a road network. This paper considers the use of the global positioning system (GPS) as one method for obtaining information on the position, speed and direction of travel of vehicles. It reports the results of a series of field studies, in which real-time GPS data were compared to data collected by an instrumented vehicle, under a range of physical and traffic conditions. The field studies and consequent data analysis provide a picture of the reliability and usefulness of GPS data for traffic monitoring purposes, and hence the possibilities for the use of GPS in IVHS projects. The use of GPS receivers tailored for mobile applications, and able to provide direct observations of vehicle speed and travel direction, coupled with database management using geographic information systems (GIS) software, was found to provide a reliable and efficient system for vehicle monitoring. Field data collection under “ideal” GPS conditions indicated that accurate speed and position data were readily obtained from the GPS. Under less favourable conditions (e.g. in downtown networks), data accuracy decreased but useful information could still be obtained. In addition, the conditions and situations under which GPS data errors could be expected were noted. The finding that it is possible to relate standard GPS signal quality indicators to increased errors in speed and position provides an enhanced degree of confidence in the use of the GPS system for real-time traffic observations.

Transport, housing and urban form: the life cycle energy consumption and emissions of city centre apartments compared with suburban dwellings

Buildings in cities and the activities carried out therein use a significant proportion of a nations energy consumption and produce substantial quantities of greenhouse gases in the process. Residential buildings are a large contributor, partially as a result of the transport and housing activities of households. In this study, life cycle analysis is used to calculate the total transport and housing energy and emissions from a sample of 41 households in apartment buildings in the city centre of Adelaide, Australia and compare them with suburban households. The purpose of this is to determine whether the urban density option of higher rise dwellings offers a lower environmental impact than conventional housing. The analysis includes delivered energy and greenhouse gas emissions generated by motorised travel and activities within the dwellings, and the energy and emissions embodied in household motor vehicles and the apartment buildings. The total delivered energy consumption of apartment households was found to be lower than suburban households due mainly to higher car usage, particularly in the outer suburbs. However, the analysis of total greenhouse gas emissions provided a somewhat different comparison especially when they were considered on a per capita basis. The total per capita emissions for apartment households varied considerably but, on average, exceeded those of both the inner and outer suburban households. This resulted from lower occupancy rates and higher emissions arising from higher dwelling operational and embodied energy consumption. Overall, it cannot be assumed that centralised, higher density living will deliver per capita emission reductions for residents, once the combined per capita life cycle emissions from housing and transport have been accounted for. A more vigorous educational, promotional and regulatory approach is required to achieve greater operational and embodied energy efficiency in apartment buildings to fully realise the emissions-reducing potential of such buildings in centralised locations.

Using GPS to Measure Traffic System Performance

Traffic system performance can be measured in various ways, but from the user perspective, congestion is the major criterion. This article examines some novel uses of GPS in the measurement of vehicle speeds and travel times and their synthesis into measures of congestion and ultimately of the performance of the urban road system. The article also will discuss the integration of GPS-based congestion measures into an ITS framework, techniques for implementing a congestion-monitoring system, and implications for urban road system planners, managers, and users.

IMPACTS OF LOWER SPEED LIMITS IN SOUTH AUSTRALIA

Australia has recently undergone a change of urban speed limits in most of its jurisdictions. The political and social shift in attitudes required for this change is significant in a country that has a strong reliance on the use of the private motor vehicle. At present five states and one territory have lowered the speed limit in urban areas from 60km/h to 50km/h. Of the remaining two states and territories, one has already implemented lower speed limits (40km/h) in small areas within cities. In the majority of cases, the only criterion for judging the success of such schemes is an observed reduction in both speeds and crash numbers. This paper reports on a more holistic assessment of such schemes taking into account factors in addition to speed and crashes including: traffic volume displacement, physical road network characteristics, environmental factors, community ownership and acceptance, enforcement effort and impact on travel times. The research work has included the analysis of extensive traffic data, community surveys and focus groups, the collection of environmental and travel time data from an instrumented probe vehicle and the computer modelling of road networks. The work reported is based on over 10 years of working with a 40km/h lower urban speed limit area in South Australia. The paper expands the notion of using speed and crash outcomes as the only criteria for measuring the success of lower speed limit schemes.

Assessing Impacts of Greenhouse Gas Abatement Measures on Urban Freight

Abstract A study to investigate the sensitivity of urban freight patterns to various greenhouse abatement policy measures is underway with Metropolitan Sydney being used as the case study area due to the availability of detailed freight and passenger network level data and models at the New South Wales Transport Data Centre (TDC). The study is designed to build on methodologies under development by TDC to derive freight traffic due to total requirements for freight and relative requirements for categories of goods from actual or forecasted commodity flows and associated information. This paper describes the selection of candidate policy measures for investigation and presents the methodology and processes used in modelling their impacts on urban freight patterns. The discussion will focus on six scenarios which provide policy instruments for application to a 1996 base case. Some results of the modelling of these scenarios will then be presented and issues arising from the study discussed. Special attention will be given to the relative changes in travel characteristics and emissions brought about by these instruments.

Meso-scale on-road vehicle emission inventory approach: a study on Dhaka City of Bangladesh supporting the ‘cause-effect’ analysis of the transport system

The study aims to develop an emission inventory (EI) approach and conduct an inventory for vehicular sources in Dhaka City, Bangladesh. A meso-scale modelling approach was adopted for the inventory; the factors that influence the emissions and the magnitude of emission variation were identified and reported on, which was an innovative approach to account emissions unlike the conventional inventory approaches. Two techniques for the emission inventory were applied, viz. (i) a combined top-down and bottom-up approach that considered the total vehicle population and the average diurnal on-road vehicle speed profile in the city and (ii) a bottom-up approach that accounted for road link-specific emissions of the city considering diurnal traffic volume and speed profiles of the respective roads. For the bottom-up approach, road link-specific detailed data were obtained through field survey in 2012, where mid-block traffic count of the day, vehicle speed profile, road network and congestion data were collected principally. The emission variances for the change in transport system characteristics (like change in fuel type, AC usage pattern, increased speed and reduced congestion/stopping) were predicted and analysed in this study; congestion influenced average speed of the vehicles, and fuel types in the vehicles were identified as the major stressors. The study performance was considered reasonable when comparing with the limited number of similar studies conducted earlier. Given the increasing trend of private vehicles each year coupled with increasing traffic congestion, the city is under threat of increased vehicular emissions unless a good management strategy is implemented. Although the inventory is conducted for Dhaka and the result may be important locally, the approach adopted in this research is innovative in nature to be followed for conducting research on other urban transport systems.

Immersion reality: combining microsimulation modelling and probe vehicles in traffic studies

A Paramics micro-simulation model of an Adelaide radial road corridor has been constructed. The corridor includes a novel one-way reversible direction expressway equipped with an advanced traffic management system (ATMS). The modelled area included two alternative radial routes: an arterial road and the expressway. The model was used to analyse the performance of the corridor when an incident occurred on the expressway, in terms of traffic conditions and greenhouse gas emissions. Real world data was collected on both routes using an instrumented vehicle which records vehicle engine, positional and emissions data in real time. Paramics allows a representation of the probe vehicle to be introduced into the simulations. The paper describes the modelled results when this vehicle was immersed in the simulation modelling on incidents and the responses of the corridors ATMS, with particular regard to the estimation of the emission impacts of ATIS and INMS.