As cities expand, conflicting issues relating to local accessibility, through movement and urban amenity require unique solutions. We can no longer provide a new expressway to ease congestion without addressing the needs of and adverse impacts on surrounding communities and public transport services.
Land use mapping, community participation and traffic modelling analysis are required to achieve a balance between competing community and congestion objectives. Without a deep understanding of how the community uses the current expressway corridor and what is important to them, transport planners cannot expect to be able to balance community needs with traffic and economic benefits of the urban expressway.
This paper will explore how identifying critical local access routes can be used to prevent potential social exclusion, enhance amenity, improve connections to community facilities and reduce the fragmentation of the surrounding suburbs.
The provision of an urban expressway needs to balance the communities’ expectations, both local and regional. Nowadays the transport planner must investigate methods of improving outcomes for adjacent communities as well as methods to ensure that developments which are stagnant or adversely impacted become reinvigorated.
The Transportation Research Board (a US based National Advisory Board to promote innovation and progress in transportation) attempted to outline principles for assessing the impacts of highway widening on
the local community. The outlined points are aimed at gaining a better understanding of community cohesion and how to minimise the impact or enhance the community outcomes, and include determination of:
To understand the impacts of an urban expressway on community liveability and cohesion is difficult because the measures are subjective and heavily affected by personal views. Therefore, the social-economic profiles of the community must also be analysed. This analysis includes mapping the areas where the communities of interest interact across the corridor and determine the need for the interaction across the corridor.
To enable balance of community best interests with congestion relief, it is suggested that the principles should also include:
Investigating would allow the transport planner to gain a greater insight into the details of the proposed expressway leading to a better strategic assessment and a better balance between the conflicting goals of community liveability and congestion.
Authorities have tried to balance both reducing congestion and providing community accessibility and liveability in the following examples:
The South Road Superway is the major north-south traffic artery through metropolitan Adelaide, Australia with a range of residential, industrial, educational and commercial land uses along its length. Congestion has been an ongoing problem and traffic volumes are predicted to increase substantially by 2031. A new freeway, the South Road Superway, has been proposed to meet the city’s need for a free flowing, non-stop, north-south traffic corridor. The South Road Superway will cater for predicted traffic volumes of 136,000 vehicles per day. As accessibility for local business owners was a major concern, a two-way, divided carriageway service road is being constructed under the four- lane, two-way South Road Superway viaduct. On and off ramps provide as much local access as possible, while the service road gives access to local properties and removes the major side friction experienced along the current road. Darlington Transport Study project at the southern end of South Road, a six-lane, extended expressway underpass or depressed carriageway is planned to cater for a predicted daily traffic volume of 89,000 vehicles per day, with a four-lane, two-way, at-grade carriageway, which is divided by the underpass, expected to carry 13,000 vehicles daily. A tram train line is also proposed as a conversion and extension of an existing rail spur.
Boston Central Artery, an elevated six lane highway designed to carry 75,000 vehicles through the centre of Boston was carrying 200,000 vehicles a day by the late eighties, resulting in heavy congestion and increasing air and noise pollution. In the mid 1980s an extensive community participation process was commenced aimed at economic growth through quality urban design to ease congestion. The result was underg rounding through traffic with increased capacity, extensive parks and open space.
I-35 Freeway through Duluth in the State of Minnesota, USA. The extension of the freeway was originally proposed as a viaduct along the edge of Lake Superior with a cloverleaf interchange in downtown Duluth. The use of the viaduct structure combined with a large sea wall was considered necessary to counteract the impact of sea spray but would have resulted in views and connections to the lake being blocked.
The road alignment and interchange would have also required the demolition of a number of historically significant buildings and important public open spaces. In the end through a more rigorous and engaging process an urban expressway that balanced good community accessibility and easing congestion was achieved.
Embarcadero Freeway, a double decker freeway in San Francisco was removed, after failure during the 1989 earthquake, and replaced with a wide boulevard.
Sydney’s Eastern Distributor, has combined tunnel, depressed carriageways and at grade sections. As part of the project local traffic management schemes were implemented, to provide an efficient transport option for through traffic to use the tolled Eastern Distributor rather than the local road network. This urban expressway includes some at grade sections which have an adverse effect on amenity through reducing cross-accessibility.
Rhode Island’s Iway project, USA involved relocating a section of the I-195 freeway with the aim of improving safety, congestion and the connections between communities. The community connection was improved by removing the existing I-195 through the downtown centre and opening up the old alignment land for development and open space adjacent to the waterfront.
Brisbane TransApex, a strategic project completed to provide various inner city tollways, and routes to ease congestion in Brisbane. This project proposed providing a number of tunnels to ease inner city congestion whilst also highlighting the potential for improved amenity and regeneration of some areas. These tunnels include the Clem Jones Tunnel and the Airport Link, which is due to be completed in 2012.
All of these examples show that an urban expressway can reduce congestion and improve the social well-being of communities, to various degrees and under certain circumstances. They indicate that there are a number of key lessons which include:
To define and identify “communities of interest” and the desired lines/ linkages to transport services, it is critical to understand potential impacts of new or upgraded roads and how to resolve or improve cross connectivity, access to services and maintain amenity. The following mapping techniques are suggested:
It is therefore important to recognise what businesses would be affected, and whether they would rely on a local community or a more distributed customer base; where they could possibly be relocated to; and what impacts will be felt by the businesses and other facilities that remain.
Understanding these types of issues before determining what access is required to maintain or enhance the local community is critical.
The use of land use mapping and analysis of the community’s social structures and requirements, and community participation is essential to determining what is important to the local community.
The balance of through traffic, commuter and freight, and local traffic is therefore important in determining what treatments should be applied to the various sections of a corridor.
To understand the need for access to and from the urban expressway an analysis of travel data is important. Using information like journey to work data, macroscopic modelling, and Origin Destination data to determine where access is provided is valuable.
The analysis of through traffic versus local traffic is crucial for determining how to access key locations. It shows the importance of maintaining a link, that could be
considered a minor arterial to ensure the necessary community connections and accessibility are maintained. This sort of analysis should also address how the community access other community facilities such as schools, health services and sporting facilities.
To maintain or enhance the current public transport use, mapping of the catchments of the bus stops as well as identifying how the travel times and facilities of the buses could be improved elsewhere in a network is important. For instance, express buses would be expected to utilise the urban expressway.
However stopping buses would need either a service road or a different route which is where mapping would be important. The mapping could be used to determine where the passengers are coming from (i.e. catchments for bus stops) and then used as a tool in the analysis of what changes in behaviour would occur if the route and/or travel time was changed.
It would also be important for understanding and making improvements to public transport services to determine if, and to what extent, congestion is eased at intersections, where the through expressway traffic is grade separated. That is, to know what downstream impacts would occur on at grade major arterials and what measures could be used to make bus routes more attractive to commuters. These measures could include bus only lanes, bus head starts at traffic signals and improved frequency amongst others.
To completely understand this issue community surveys and participation would be required especially to understand routes and current impacts of the existing grade separations.
Another aspect of the active transport that needs to be considered is where access to the corridor is provided. Even if road closures are required to restrict vehicle access there is no reason to block the active transport access. Also, through mapping of pull factors and community views, links across the corridor could be identified and provided. This combined with urban design and application of Crime Prevention Through Environmental Design (CPTED) principles could provide greenway links on both sides of the corridor increasing both pedestrian and cyclist activation along the corridor and improving outcomes, especially for commuter cyclists.
Analysis of the impact of an urban expressway on freight routes is important from a number of perspectives. Firstly from a strategic point of view, to determine whether the resultant improved travel times to the origins and destinations of these trips. Secondly, to assess whether this would cause an increase of freight traffic on other roads and provide a catalyst to redevelop inner city industrial areas due to their improved accessibility.
To minimise the impact of the urban expressway, communities of interest should be identified and where these communities of interest occur, greater care should be taken with the planning approach.
At grade solutions can sever community cohesion so other treatments including viaducts, tunnels or other grade separations that allow the community to cross the corridor, or travel along the corridor would be preferred. These solutions could be combined with various at grade solutions including service roads with wide pedestrian and cycling paths,
or the provision of new development along (or on top of) the corridor to enhance the amenity and viability of the corridor.
By undertaking the necessary research into the community and through community participation there is an opportunity for the community to highlight what public facilities (parks, open space etc) would benefit the community which could then be incorporated into the overall redevelopment of the corridor.
Other potential treatments for areas identified as communities of interest is to utilise a redevelopment mechanism. This means that rather than just acquire the property required to allow for the expansion, additional land could be acquired to produce transit oriented developments with open space provision and connection for pedestrian, cyclists, public transport and local traffic.
To improve the patronage of the public transport, the community would need to see benefits in costs (ticket vs. parking), increased frequency or time savings in other sections of the network. The potential solutions include bus lanes on intersecting arterials on the up and downstream sections of the road network, higher frequencies and cheaper services. Along the corridor, the need to provide services is important, for instance one lane in each direction could be dedicated to buses (at grade) ensuring reasonable travel times and enhancing the services for the communities adjacent to the corridor.
Active transport across the corridor would require pedestrian bridges if at grade or depressed carriageway are the treatment for the expressway. This type of treatment results in community fragmentation and should not be used in areas were strong community cohesion exists but could be used where linkages are less critical or open space is provided on either or both sides of the corridor.
Other treatments for active transport include “green” linkages for pedestrians and wide cycle lanes or paths to enhance the amenity for commuter cyclists. These potential treatments would need to be based on the mapping techniques as well as social-economic analysis and community participation to ensure they would be fit for purpose and improve the liveability of the community.
About Leigh Dawson
Leigh Dawson has a background in strategic transport planning, concept and detailed design of roads and intersections in urban and rural locations. He is experienced in traffic engineering, conducting road safety audits and restricted access vehicle route assessments.
About Richard Hanslip
Richard Hanslip has been a traffic and transport consultant for the duration of his 40 year career, covering all aspects of traffic engineering and transport planning. He has a working appreciation of transport planning and environmental issues and projects, having worked on a range of multi-disciplinary transport projects, including those with sensitive public or government issues and of considerable complexity.