La battaglia per la strada – Parte I

Earning a Public Space Dividend in the Streets

– Paul Barter, Lee Kuan Yew School of Public Policy, National University of Singapore

Abstract: Experiments with “shared space” have captured imaginations and considerable media coverage in recent years. Most of the excitement stems from surprise that streets without kerbs, road markings or signage can work well and achieve “safety through uncertainty”. This paper looks at another equally important insight from shared space.

(Questo articolo è apparso su World Streets oggi e, in assenza dell’editore di NM che si sta godendo le meritate vacanze, è stato postato qui nella versione originale inglese. Una versione tradotta ed adattata sarà disponibile in luglio. Grazie per la vostra pazienza.)

* Clicka qui per avere una traduzione automatica approssimativa ma leggibile

It focuses on a series of innovations that, like shared space, re-arrange the roles of streets in new ways to yield a “dividend” of expanded urban public realm, with little or no loss of transport utility. Such a space dividend should be especially welcome in dense cities that are both congested and short of public space.


What are streets and roadways for? An obvious answer is traffic movement. But that is clearly not the whole story. A second role is to allow the reaching of final destinations— the role we call “access”. Thirdly, streets can be valuable public places in their own right. In addition, moving high-speed motor vehicles differ enormously from movement by low-speed, vulnerable modes such as bicycles. Unfortunately, speedy motor traffic movement and the other roles of streets are in serious conflict. For almost a century, the tension between these roles has been at the heart of debate over street design (Hass-Klau 1990; Jacobs et al. 2002). This article reviews emerging resolutions to this tension.

The Battle for Street Space

The essence of a street is that it serves all these roles simultaneously—providing for traffic movement and access, and as public space for urban activities. However, mainstream roadway management has spent many decades seeking, like Le Corbusier, the “death of the street”. It tends to turn everything between kerbs into “traffic space” where motor vehicle movement is the design priority (Patton 2007).

Motorised traffic, slow modes and pedestrians are strictly segregated in both space and time. The role of streets as “public realm” has been largely restricted to the pavements (sidewalks) and to pedestrian zones. Most cities are desperately short of attractive public space and space for the networks needed by the gentle but vulnerable modes such as walking and cycling.

Since the 1930s, traffic engineers have routinely classified every roadway in a hierarchy according to the degree to which it serves either traffic movement or access. Major arterials and expressways which are at the top of the hierarchy are managed primarily for maximum vehicle mobility. Any access functions are carefully limited to contain “friction” with the mainstream traffic. Only streets at the lowest level of the hierarchy are used mainly for access. Furthermore, the planning process often seeks to remove as much activity as possible (and hence, the “public space” role) from roadways and their vicinity. The influential UK report of 1963, Traffic in Towns by Colin Buchanan, reinforced the idea that segregation was essential (Hamilton-Baillie 2008).

The roadway hierarchy has no place for streets that serve both traffic and multiple other purposes (Svensson 2004). Yet, traditional urban streets and main streets remain ubiquitous. They provide (inadequately) for both access and mobility and are sites of perennial conflict. Such conflict is especially obvious in the heavily used streets of many dense Asian cities. The conventional traffic engineering approach offers little guidance for such multi-role streets (Svensson 2004).

Expanding Public Realm without Evicting Motor Vehicles

Recently, a series of promising street management innovations has emerged that re- assert in new ways the multi-purpose nature of the street. (See Box Story “Innovations that Expand Public Realm in the Streets”.) They offer ways to increase the public realm without removing the motor vehicles or seriously undermining the utility of the motorised traffic system. Does that sound too good to be true?

These innovations exploit common insights and principles. First, they involve making a strong distinction between “traffic areas” or “highway” and public space or the “public realm” (Shared Space project 2005). Traffic areas are the realm of conventional traffic engineering where high-speed motor vehicle movement is primary, with its flow carefully segregated from slower users like pedestrians and cyclists.

Second, some of this redefined “public realm” can be shared. It includes new spaces designed for the peaceful co-existence of public place activities, slow movement by vulnerable modes as well as motor vehicles, especially those seeking access to the vicinity. The key to such co-existence lies in keeping speeds low, ideally to no more than about 30 km/h (Shared Space project, 2005). Low speeds mean that motor vehicles need not be excluded but those present will mainly be making access movements or on the “last mile” (or the first) of their trips.

Third, these innovations shift the boundary between public realm and traffic space, so that a surprising amount of what we now think of as traffic space becomes part of the low-speed public realm. In shared spaces and in other slow zones, such as Tempo 30 zones and bicycle boulevards, whole streets and intersections are converted to public space. In multi-way boulevards, public realm includes everything from the building line to the outer edge of the central, high-speed traffic lanes. This newly expanded public realm serves local motor vehicle access, slow-mode movement, public space roles and sometimes some through-traffic (with low priority and at low speed). Only the high-speed traffic movement is excluded and kept within traffic space.

Fourth, a key design goal is that both the public realm and traffic space should work better by being kept distinct (Shared Space project 2005). Cities still need high-speed traffic space of course, just as some pure pedestrian space must also remain. But a surprising amount of shared public realm could be reclaimed without diminishing total traffic capacity. The key is that most of the expansion of the public realm envisaged here would take over traffic space that does not work very efficiently anyway. For example, the capacity of many of today’s motorised traffic lanes is reduced by turning movements, kerbside drop-offs, parking, loading and other street activities. After transforming such spaces into public realm, the remaining traffic space can be re-designed more thoroughly for its traffic function. Moreover, the new public realm retains some traffic function, albeit at low speed, as a safety valve at times of extreme congestion.

A high percentage of traffic volume in most cities is carried by roads at the top of the roadway hierarchy. Much of the remaining traffic is in fact short-distance traffic, or is on the first or last “mile” of a longer trip, or is circling for a parking spot. Such traffic does not need high speeds. In fact, a slower environment is more appropriate for access movement. Furthermore, although public realm requires very low peak speeds, the approaches discussed here also usually reduce the need for stopping and starting, so that average speeds and travel times are often little changed. Therefore, reclaiming such space as public realm has less impact on traffic performance than one would think based purely on the percentage of traffic space “lost”.

Expanding the low-speed public realm would also allow us to be much more tolerant of a diverse range of small, vulnerable vehicles that currently do not fit easily into our transport systems. These include bicycles, in-line skates, skateboards, kick scooters, wheelchairs and many other “Personal Mobility Devices”.

Barriers to Change

As with most innovations, change will take more than a simple policy decision. In most countries, roadway management practices are deeply embedded in institutions, their missions, objectives, performance-measures and boundaries of responsibility between agencies; in professional guidelines, codes and design standards; and in traffic rules and road user education.

Fortunately, little change is needed in conventional roadway management when it is applied to its appropriate domain i.e. the highspeed arterials and highways. It is only within an expanded public realm and at its boundaries that drastic change is called for. Standard practice must no longer apply to such spaces. Level of service (LOS) has no place here. Nor do conventional approaches to road safety, such as removal of “fixed hazardous objects”. Roadways that form part of the shared public realm should not resemble highways despite the presence of motor vehicles. Design principles for such streets, including signage and road markings, must be different from those for traffic space.

The public realm of streets needs a whole new set of procedures, guidelines and metrics of success. More research is needed to develop them. This is beginning to happen through experimentation in many countries (Shared Space project 2008; Hamilton-Baillie 2008; Jacobs et al. 2002). The Netherlands, Sweden and the United Kingdom have revised their guidance manuals on street design (e.g. DfT 2007). Traffic engineers will need to adapt their problem solving to the special challenges of designing shared public realm. They will need to collaborate more with urban design professionals and urban planners, who will also need to take more interest in the streets that they have long neglected.


This article has provided a quick review of promising new ways to reconcile movement, access and place-making within our precious urban rights of way. New public space is gained through including low-speed access movement by motor vehicles within the public realm. It is this “public space dividend” that has been my focus. It may be too soon to tell if these ideas can deliver on their promise. We may only find out by trying them out.


This article was first published in the May edition of JOURNEYS, an Academy publication of the Land Transport Authority of Singapore(LTA). We thought that many of our readers might not have picked it up, so we are most pleased to reprint here with their kind permission and that of the author.

Paul Barter is an Assistant Professor in the Lee Kuan Yew School of Public Policy, National University of Singapore where he teaches infrastructure policy, urban policy, transport policy and an introduction to public policy. He has published studies of transport policy in Kuala Lumpur and Singapore. His current research interests are in innovation in transport demand management, public transport regulation, and contested priorities in urban transport policy.



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