Trip generation of retail developments in Singapore

Institute of Transportation Engineers. ITE Journal, Sep 2001 by Fan, Henry S L, Tan, Yan Weng

TRIP-GENERATION RATES USED FOR WESTERN CITIES MAY NOT BE APPLICABLE TO ASIAN CITIES AS THIS STUDY OF RETAIL SITES IN SINGAPORE INDICATED THAT WESTERN RATES ARE HIGHER.

A CONSIDERABLE AMOUNT OF research has been done on trip generation of various land uses in North America and Europe, but few studies have been conducted for Asian cities. The prediction of traffic impacts of proposed developments in these cities is often based on rates developed for western conditions, such as those reported by the Institute of Transportation Engineers (ITE)1 and the Institution of Highways and Transportation (IHT).2

Trip-generation characteristics vary significantly from one area to another due to differences in levels of vehicle ownership, public-transport service, land-use planning, travel behavior and traffic-management measures. Hence, values developed on the basis of western conditions may not be suitable for use in Asian cities.

Singapore is one Asian city where the rates developed on the basis of western conditions may not be applicable. First, Singapore has implemented a number of traffic-management measures3 to contain congestion. These measures, which include ownership restraints such as the vehicle quota scheme and high vehicle taxes, as well as usage restraints in the form of high road taxes, gasoline taxes and road pricing, are not generally found in western cities.

The road-pricing system (known formerly as the manual Area Licensing Scheme) was originally implemented for the central business district (CBD). It was replaced in 1998 by an automated electronic road pricing (ERP) system. ERP has now been extended to cover also some stretches of the expressways. Under the ERP, overhead gantries are placed at the entry points to the CBD and to the expressway sections. During the restricted hours, drivers of vehicles are charged for the use of the road space when their vehicles pass these gantries. These restricted hours do not apply on weekends and public holidays.

The vehicle-restraint measures have kept car ownership at rather low levels. In 1997, Singapore had 373,345 cars for a population of 3.737 million,4 or an average car ownership rate of 0.1 cars per person. Compared with the 1988 level, the ownership-- restraint measure had resulted in only an increase of about 11 percent in average car ownership in Singapore, or an average increase of just 1 percent per annum over this period. Such a level of car ownership is substantially lower than those in western countries. For example, the car ownership levels in 1995 in Canada, France, Germany (West), the United Kingdom and the United States ranged from 0.355 to 0.517,5 or about 3.5 to 5.1 times that for Singapore.

Second, Singapore is a small island state where the trip lengths are quite short relative to those of western urban cities. A large fleet of taxis and rather cheap fares (due to the short trip lengths) results in relatively high usage of taxi services. Singapore also has an extensive public-transport network of buses complemented by a mass rapid transit (MRT) system that is used by a majority of the population. In 1995, 51 percent of the 7 million daily trips made by motorized means were on public-transport modes.6

These conditions are quite different from that in many of the cities in the West. Therefore, it is desirable, for site-planning and traffic-impact analysis, to have trip-- generation rates of major land uses that are more suitable for local conditions. Since 1992, the Centre for Transportation Studies at Nanyang Technological University has embarked on a study to establish traffic- and parking-generation rates of major land uses in Singapore. Prior to this study, very little data existed in Singapore to make meaningful assessments of traffic generated by various developments. To date, the study has covered retail, office, industrial, technology parks and educational land uses. It is hoped that results from this study will have practical applications for transport planners and engineers not only in Singapore but also cities in other Asian countries that share similar characteristics.

This feature reports the development of models for estimating vehicle trip-- generation rates of retail land uses in Singapore. The retail land uses covered in this study are primarily shopping centers and specialty retail centers as per the ITE classification. An evaluation of the effectiveness of two different methods of estimating trip-generation rates is also presented.

STUDY-SITE SELECTION

Three criteria were used in selecting the sites for this study. These were: (a) each site should have a predominant retail land use; (b) the site should be free-- standing with separate parking facilities; the driveways at each site should only serve that site and not adjacent properties; and (c) the site should be close to fully (at least 90 percent) occupied.

Many retail developments in Singapore often also contained nonretail uses such as offices, computer schools, or residential apartments. Hence, it was difficult to find many "pure" retail sites. This is not unique to Singapore. For example, ITE stated that some of the shopping centers in their data-- base also contained nonmerchandising facilities such as offices, movie theaters, post offices, banks, recreational facilities, etc.1 For the purpose of this study, it was considered acceptable to allow for some proportion of nonretail uses on site.