Academic journal article The Town Planning Review

Quantitative Assessment of Urban Road Network Hierarchy Planning

Academic journal article The Town Planning Review

Quantitative Assessment of Urban Road Network Hierarchy Planning

Article excerpt

The functional classification of urban road networks has a long history, and it is significant in modern transport and town planning. In order to closely monitor the implementation in practice, quantitative assessment of the performance of road functional classification is essential for transport authorities in road investment, maintenance, design and operation. However, studies in this field are few. In this context, this article proposes a method for quantitatively assessing urban road networks. The assessment framework consists of eight mathematically formulated indicators; the inputs required are GPS data, data from taxi-fare meters and GIS data (or digitalised road network maps). Continuing the discussion on a theoretical level, an experiment of the proposed method is conducted using a dataset collected in Beijing. The insightful findings concerning the performance of road functional classification in Beijing illustrate the usefulness of the method.

Keywords: road network planning, functional classification, hierarchy, mobility, accessibility, GPS/GIS

(ProQuest: ... denotes formulae omitted.)

1 Introduction

Road hierarchy (RH)/functional classification (FC) plays an important role in shaping urban area layout and channellising traffic flows. As defined by the United States (US) Department of Transportation Federal Highway Administration (FHWA) (1989), road functional classification is: 'the process by which streets and highways are grouped into classes, or systems, according to the character of service they are intended to provide' (http://www.fhwa.dot.gov/environment/publications/flexibility/ch03.cfm). The establishment of the concept can be traced back to 1963, when the well-known report Traffic in Towns, prepared by Colin Buchanan for the United Kingdom (UK) Ministry of Transport, was published. In his report, Buchanan stated: 'basically ... there are only two kinds of roads - distributors designed for movement, and access roads to serve the buildings' (UK Ministry of Transport, 1964, 44). This is considered to be the fundamental principle for road functional hierarchy, and it has been widely accepted and implemented over the years in road-network design throughout many countries, although adaptations were made in some cases.

Now, almost every road network in the world is organised to include a number of functional systems in a hierarchical way. For example, the roads in the UK are classified as primary distributors, district distributors, local distributors, access roads, pedestrian routes and cycle routes (IHT, 1997); the French road system consists of autoroutes, route nationale, routes départmentales and routes communales; in the US, urban roads consist of principal arterials, minor arterials, collector streets and local streets (FHWA, 1989); in China, there are four levels of urban road (PRC Ministry of Construction, 1995a), equivalent to the four levels of the US system.

RH/FC has a significant impact on many aspects of transport planning and management, including the strategic design of road networks, levels of road maintenance, ranking of construction work, investment in infrastructures, etc. It also has close connections with town planning. As English Partnerships and Davies (2000) state: 'towns exist for interaction' (69); indeed: 'they depend upon movement systems - roads, streets, footpaths and public transport routes' (69). While movement systems are an important element in the existence of towns, RH/FC planning is an important task in designing movement systems. RH/FC may impact on land use both directly and indirectly (Litman, 2012), as the development of transport facilities not only needs land, it also affects the development of land use. According to the Transportation and Traffic Engineering Handbook (Pline, 1999), RH/FC plays a very important role in urban sprawl. Meanwhile, urban layout and land use also significantly affect road function. Inappropriate land use prevents roads from functioning as they are intended. …

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