Pedestrian Safety Versus Traffic Flow: Finding the Balance

Abstract

Pedestrian safety is an issue in many urbanized areas throughout the world. While this is recognized by policymakers, many tend to focus more on traffic congestion and finding solutions to improve traffic flow. These two objectives are often in conflict in urban areas. This paper outlines the early history of this conflict in Great Britain and the USA leading up to the development of engineering guidelines focused on improving traffic flow and the level of service in cities, guidelines that are replicated in many developing countries. New safety manuals are being developed and some of the flaws with these are also highlighted, primarily that they tend to ignore behavioral adaptation that can occur in response to safety policies. This is followed by a review of research examining safety trends and policies that have successfully reduced fatalities. This research also suggests that the construction of large arterial and collector roads is counterproductive, despite the recommendations in engineering guidance. Pedestrian casualties and their severity are then discussed, with findings that show that larger, high-speed roads tend to result in more severe injuries and that various features of urban environments are beneficial for pedestrian safety. Various problems with the data available for conducting this type of analysis, especially pedestrian fatality data, make the rigorous tracking of such information problematic. Solutions to improving traffic and pedestrian safety are then highlighted, including shared space concepts, complete streets, and road diets that reduce the flow of traffic. A cost/benefit analysis of a road diet is evaluated showing that for the case studied, the safety benefits are overwhelmingly positive, with only minor costs associated with extra traffic delay. In closing, the implications for rapidly developing countries are briefly discussed with a warning not to follow the path of some western countries.

9.1 Introduction

Modern and developing cities are characterized by the pervasiveness of motorized traffic. Western nations began this process over a century ago when motorized vehicles originally became commonplace and ownership and use grew rapidly. Over the last 20–30 years, many rapidly developing nations are facing the same growth in motorized vehicle usage and are facing many of the challenges that the developed world tackled in the past. While there are well-known benefits to motorization, there are also costs. Many countries are making the same mistakes that western nations have been trying to fix over the last few decades. The promotion of mobility and traffic flow over other goals is now seen as having damaged the well-being of cities mainly by taking space away from people with consequences on the ability of people to walk and engage in activities without motorized transport.

This chapter provides an overview of the conflict between pedestrian safety and designing and building streets to maintain efficient traffic flow. I start with an historical perspective on the early conflicts over the use of streets in both Great Britain and the USA. This is followed by a discussion and critique of the guidance developed by traffic engineers to improve traffic flow and more recently traffic safety. The effectiveness of various approaches to improving both traffic and pedestrian safety is then discussed, based on recent research, while noting that in the USA, our safety data still has many problems. Conclusions focus on solutions with a spotlight on shifting more street space to pedestrians as a way of improving both safety and the livability of cities. The results of a cost/benefit analysis of one specific approach, a road diet, that reduces vehicle capacity is presented and shows overwhelming positive benefits. I close with some discussion of how developing nations can tackle these issues before it is too late.

9.2 A Brief History Lesson

Starting in the mid-nineteenth century, before motorized vehicles, conflicts began to develop over the use of city streets in Britain. Horse-drawn carriages (also known as omnibuses) became much more common as incomes grew with the industrial revolution. Pedestrians dominated city streets and these new forms of transport were a hazard resulting in both fatal and injury crashes. As early as 1840, there were about 1000 deaths recorded and fatality rates averaged about 50 per million (Hair 1971; Ishaque and Noland 2006). For comparison, the rate in 2013 was about 26.72 per million (based on 1713 road deaths) (Department for Transport 2013). While data records in the nineteenth century may not be accurate, this implies that the fatality rate associated with road transport has only been cut in half in 170 years; however, mobility is vastly improved and we will return to this trade-off later.

Those responsible for traffic casualties were liable to have their vehicle forfeited under British law. This was known as the Law of the Deodands, and objects involved in the death of a person were forfeited to the Crown. This law, however, was repealed in 1846, just at the time that deaths from traffic were increasing. The reason for this was that jurors often did not convict the vehicle owner, partly because they owned vehicles themselves and they saw the forfeited items ending up with “lords and churches instead of with the family of the deceased.” (Ishaque and Noland 2006; Farr 1870). This shows how those who were more mobile (and normally more privileged people sat on juries) sought to minimize the penalties associated with the benefits of mobility. This persists to this day, in that penalties for vehicle drivers who kill pedestrians are often trivial.

It also suggests that pedestrians were considered to be more blame-worthy for their fate than the drivers of carriages and omnibuses. The right to the mobility of these vehicles was seen as more important than the safety of those who were walking. One jurist wrote in 1869: “Accidents happen because the drivers do not believe, or at any rate will not admit, that foot passengers had as much right to cross a street or thoroughfare as persons driving has to pass along it.” (Ishaque and Noland 2006; The Times 1869). This sounds very familiar to debates that we hear today over the use of road space. Recent research suggests that attitudes towards the deaths of vulnerable road users have not changed (Goddard et al. 2019; Ralph et al. 2019).

As traffic increased, policy and regulations were developed to both protect pedestrians and guarantee the ability for traffic to flow unimpeded. Three approaches in particular were followed in Britain. These were the requirement that footpaths (sidewalks) be built along streets, the development of traffic signals and ways for pedestrians to cross streets, and the building of guardrails along sidewalks to channel pedestrians to designated crossing points.

Sidewalks are undoubtedly useful for protecting pedestrians from fast-moving traffic, but also allow that traffic to move in the street by removing the right of pedestrians to walk in the street. A 1906 letter published in the Proceedings of the Institute of Civil Engineers sums up the attitude: “It is unfair to the motor car driver, as well as to the pedestrian, to allow any important road to be without a footpath” (Ishaque and Noland 2006; Lindsay 1905–06). Design standards for footpaths in London were quite liberal, requiring that they have a width that is 1/6th of that of the total carriageway. The latter were often 24 ft (7.3 m) in width; thus, the footpaths were at least 4 ft (1.2 m) in width on both sides of the street (Ishaque and Noland 2006). Footpaths were also seen as a sanitary measure to improve drainage and to bring more order to city streets, especially in the slums (Ishaque and Noland 2006).

The first traffic signal started operation in 1869 in front of the Houses of Parliament in London. This was a gas-fired semaphore, similar to railroad signals. It provided a 30 s window for pedestrians to cross every five minutes. This made compliance by pedestrians unlikely as the wait time was long and most carriage drivers also did not stop, given their unfamiliarity with the new technology. The signal itself suffered from several gas explosions. In any event, the experiment was discontinued in 1870 as many Members of Parliament protested (Ishaque and Noland 2006).

After the failure of this experiment, debate turned to other means for pedestrians to safely cross streets while allowing traffic to flow unimpeded. Police officers often guided pedestrians across streets, but this was seen as costly. Subway tunnels and footbridges were considered. The latter were considered to be unsightly and land acquisition costs would be high. The first pedestrian subway was opened in 1870 (near the failed semaphore). Many of these were built in London in subsequent years, but debates over the best means for pedestrians to safely cross streets continued. There was a recognition that many people would still cross at street level even if a subway tunnel or footbridge was present. Well into the twentieth century, there was little consideration of simply stopping traffic at key pedestrian crossings, suggesting that traffic flow was more important than providing safe pedestrian crossings (Ishaque and Noland 2006). Adding to the debate was the concern expressed in this statement before the House of Lords in 1938: “We do feel that if subways and bridges were put into general operation it would only confirm the view of the motorist that the public highway was a motor speed track and would lead to further accidents.” (Ishaque and Noland 2006; House of Lords Sessional Papers 1938).

The other engineering measure taken was the installation of guardrails along sidewalks and also within median refuges. These served the purpose of keeping pedestrians from entering the street and also channeled them to designated crossing points. By assuring that pedestrians could no longer enter the street, this facilitated the free flow of traffic. These were widely built in the 1930s as motorized traffic increased, some as much as three miles long on some East London streets. These were very effective at keeping pedestrians out of the street. By the 1930s, the conflict between which mode dominates the street and what the purpose of the street was had clearly been decided in favor of the motorcar at the expense of the pedestrian.

A similar story was playing out in the USA, as documented by Peter Norton in his seminal book, Fighting Traffic, The Dawn of the Motor Age in the American City (Norton 2008). In the 1920s, the main victim of increased motorization was children. The vast majority of traffic fatalities in cities were pedestrians (e.g., in Philadelphia, pedestrians accounted for 75% of total traffic fatalities) and about half of these were children (Norton 2008). Children and their parents were used to the streets being places where children could play and wander freely. But with the danger introduced by motorized vehicles, there was outrage at the carnage that was occurring. In some cities, monuments to children slain by vehicles were erected as shown in Fig. 9.1 (Norton 2008).¹ As parents protested the conditions, the motor vehicle industry fought back and defended the “rights” of the population to be mobile. Some cities considered implementing speed restrictions. In 1923, Cincinnati, Ohio, debated an initiative that would have required speed governors in all vehicles. In response, the motor industry developed a strategy of shifting blame to pedestrians and children, implying that parents were irresponsible to let their children play in the streets. They created the term “jay-walker” to mock pedestrians who did not cross at designated crossing points; in fact, one year after the Cincinnati initiative failed, Los Angeles passed the first law against jay-walking. As in Great Britain, by the 1930s, the battle over the use of street space had been decided with the motorcar firmly in control (Norton 2008).

Fig. 9.1

(source Norton 2008)

Dedication of children’s memorial, Baltimore, MD, 1922

9.3 Engineering Guidelines

In the 1920s, as motor vehicle traffic rapidly grew, cities were confronted with the problem of vehicles congesting central business districts. In response, and frequently at the behest of the business community, municipal engineers (the forerunner to today’s traffic engineers) sought methods to improve the efficiency of traffic flow. As discussed above, one means was controlling pedestrian movements. Many engineers also saw the provision of more electrical transit systems as one way to improve efficiency. But other engineering approaches were also tried, including coordinated traffic signals (in Chicago), eliminating on-street parking, and ultimately reconfiguring the city itself to provide more road capacity for vehicles (Norton 2008). As early as 1925, the first formal engineering guidebook, Street Traffic Control, was produced (Norton 2008).

After the Second World War, growth in vehicle ownership accelerated. The Highway Research Board (forerunner to the Transportation Research Board) produced the first version of the Highway Capacity Manual in 1950. Updates have been produced every few years (the current being 2010). In 1965, the concept of “level of service” was introduced. This was a means of classifying the travel delay associated with highways and intersections. Underlying the concept is detailed calculations of traffic flow, queueing, and signal timings, but the output produces a simple A to F ranking of the level of service (A being the best, and F being the worst). In practice, C provides a reasonably stable flow of vehicles, and most traffic engineers become concerned only at levels of D and lower. For intersection level of service, the rankings are linked to estimated delays for both signalized and unsignalized intersections (see Table 9.1).

Table 9.1 Level of service (LOS) at intersections (Transportation Research Board 2010)

Level of service (LOS) requirements have been extremely influential. In most, if not all, major cities and towns in the USA, any new development requires an analysis of LOS. If a new development (or redevelopment) leads to a degradation of LOS, usually below C, then the developer must either scale back the size of the development or fund mitigation measures such that there is no reduction in level of service. These measures may include increases in the width of the road, changes to the turning lanes at intersections, or installation of traffic signals. The incentive for the developer is frequently to simply build in an area with minimal existing traffic on the edge of the urbanized area; in other words, this encourages sprawling development patterns. But mitigation measures in developed areas make the pedestrian environment less friendly, such as increasing the time needed to cross streets, or by encouraging faster traffic speeds from widening the road, or installing turning lanes.

Thus, engineering guidelines as implemented via LOS requirements became the foundation for how cities grew after the mid-1960s. In 2015, some fifty years after their promulgation in the Highway Capacity Manual, there is debate over the value of using this metric as the only performance criteria for both changes in street design and land use. In California, environmental legislation required a LOS analysis for all new developments, leading in most cases to worse environmental outcomes as new development located in areas where there would be no impact on existing traffic. In 2008, legislation was passed in California that allows development in “transit-rich” or infill areas to not be subject to this requirement.² Further legislation in 2013 formally removed the LOS requirement and many cities have moved to metrics based on vehicle-kilometers of travel (Lee and Handy 2018).³ While the impact of this change is still being assessed, it is seen as a way to reduce road design changes that benefit the motorist, while making the streets more walkable.

Another important guidance document is “A Policy on Geometric Design of Highways and Streets,” aka “the Green Book,” produced by the American Association of State Highway and Transportation Officials (AASHTO 2011). This guidance document sets standards for how highways should be built, such as the width of traffic lanes, the curvature, and a large variety of other detailed design components. This has resulted in the design and construction of highways and streets that are “wider, straighter, and faster,” primarily because these are seen as being both efficient and safe highways. As Dumbaugh and Gattis (2005) show, the concepts of rural road arterial design have been applied to urban streets, while forgetting that on urban streets, pedestrians are present, and the function of the road is very different than in a rural area. The Green Book has little consideration of the role of pedestrian movements, although the most recent guidance does recognize that pedestrians provide vitality to central business districts and thus should be catered to (AASHTO 2011). Much of the limited discussion on safety issues in the Green Book is dedicated to creating “clear zones,” that is, a buffer whereby vehicles running off the road do not hit obstacles (e.g., trees). While the guidance recognizes this may be difficult to do in urban areas, it still recommends doing as much as possible to remove roadside objects, precisely those that may protect pedestrians walking on sidewalks (AASHTO 2011).

The Green Book now defers much of the safety guidance to the newly developed Highway Safety Manual, published by AASHTO in 2010 (AASHTO 2010). The purpose of the manual is to provide practicing engineers with crash reduction factors (CRF) for different road types, so that these can be used in cost/benefit analysis of safety improvements. CRFs are basically coefficient estimates derived from statistical crash frequency models.

While it is commendable that there is now a concern for traffic safety, there are several problems with the approach being taken. The CRFs are assumed to be point estimates. That is, the uncertainty inherent in any statistical estimate is ignored. Another issue is that contextual issues are ignored; the CRF estimates may not include other factors associated with crash occurrence, possibly leading to biased estimates (Noland 2013; Mitra and Washington 2012). Research work we recently completed suggests that omitting variables that provide contextual information on an area increases the parameter estimates associated with various road design features. In other words, we are probably overestimating the benefits of design treatments relative to other risk reduction policies (Noland and Adediji 2018). The risk to cities is that once the HSM is put into widespread use, traffic engineers and decision makers will follow the guidance without considering its limitations and other contextual features of the urban environment.

The research underpinning the CRFs is also questionable. For example, Noland (2013) attempts to find the source of the CRF for rural two-lane roads, an area that has been researched to a large extent due to the prevalence of crashes on these roads. Tracing back the citations for the CRFs, the HSM refers to two studies: (Zegeer et al. 1981; Griffin and Mak 1987), but it is not transparent how these studies were used to derive the CRFs, and both suffer from major methodological flaws (Noland 2013). The CRFs for rural two-lane roads in the HSM are shown in Table 9.2 and as can be seen imply that wider roads are safer, especially for larger traffic flows. It is not reported whether there are any statistically significant differences between these estimates and it is also assumed that one can linearly interpolate between them, which (Persaud and Lyon 2007) suggests is not appropriate. Other work has questioned whether there is any safety benefit from wider lanes, even suggesting that crashes may increase (Noland 2003; Hauer 2005; Milton and Mannering 1998). Therefore, developing strict criteria of this type may be counterproductive and actually undermine the goal of improving safety. Our research suggests that there are wide error bars for any mean estimate (Noland and Adediji 2018).

Table 9.2 Crash modification factors from the highway safety manual (AASHTO 2010)

The development of the Highway Safety Manual poses a risk to planners and those concerned with reallocating space to pedestrians. By promulgating engineering guidelines that ignore contextual features, and which may not even be estimated correctly, decisions may be made that at best have no beneficial safety impact, and at worst, actually increase traffic risk, especially to pedestrians, and reduce the mobility of pedestrians.

9.4 Behavioral Adaptation

Efforts to improve the safety of vehicles and streets would seem like an uncontroversial topic. Everyone benefits when safety is improved, especially when the costs of those improvements are small. However, it is not clear that all safety improvements result in reductions in the number of injuries and fatalities. This is because people change their behavior in response to improved safety. This concept is known as “risk compensation” by economists (Peltzman 1975) and “risk homeostasis” by psychologists (Wilde 1982) and more generally defined as “behavioral adaptation” (Noland 2013). There is a long history of debate over the theory, with many safety researchers questioning the basic theory (Robertson 1981; Graham and Garber 1984). At the same time, there has been much research confirming the basic process and further theoretical extensions have incorporated “task homeostasis,” that is, the difficulty of the task involved with maintaining safety (Fuller 2005).

Noland (2013) provides a full review of these issues and reframes the concept as a trade-off between safety and mobility. In this sense, the relative safety of travel or of any given mode is simply another attribute that people consider in their choice process. A key trade-off is the relative time devoted to a trip versus the safety of that trip; all else equal, faster speeds are riskier but reduce travel time. A pedestrian seeking to cross a busy road when traffic is approaching is merely seeking to minimize the travel time associated with his/her trip.

This framework is displayed in Fig. 9.2, reproduced from (Noland 2013). If a policy or technology is able to improve safety, the increased level of safety may lead to more mobility or more safety. That is, some of the safety improvement is converted to more driving which may offset some of the benefits of the improvement. Individual behavior may be seen as more risky, such as faster speeds, but if the vehicle is more crashworthy, the driver is simply making a rational decision to reduce his/her travel time. Other behavioral adaptations can also occur, such as driving less attentively, or engaging in other activities while driving (e.g., speaking or texting on a mobile phone). Referring back to Fig. 9.2, if one is initially at point A with a given level of mobility and safety, a change in policy or technology can improve safety for a given level of mobility (represented by the shifted curve). Point B would represent a case where all of the improvement is converted to increased safety, while point C represents the case where some is taken as a mobility increase. Point D might represent the case where safety declines, perhaps because driver’s have a high preference for increased mobility (or their perception of the safety improvement exceeds its actual level).

Fig. 9.2

(source Noland 2013)

Trade-offs between safety and mobility

With these trade-offs in mind, it is easy to understand the decision making process of pedestrians. While the Green Book states that “pedestrian actions are less predictable than those of motorists” (AASHTO 2011), in reality pedestrians are making rational choices. Most do not take unnecessary risks but balance the costs and benefits of their actions. Seemingly risky choices are merely a decision to reduce travel time. When these risks are misperceived, whether due to fatigue or a cognitive deficit, then crashes are more likely to occur.

9.5 Data Issues

A major issue with safety data is its quality (O'Day 1993; Shinar et al. 1983). While it is well recognized that fatality data is generally of higher quality, less severe crashes typically are underreported or not fully investigated. Given the rhetoric that transportation agencies cite about the need to improve safety, it is somewhat astounding that there remain major data deficiencies in the USA. Recent work we have done indicates that there are likely major issues with pedestrian fatality data, ranging from how these are recorded and processed to how pedestrians are classified. There is also a lack of transparency with many State Departments of Transportation not making their crash data available to the public.

A recent analysis of New Jersey pedestrian fatality records using original police records suggests that out of 157 total reported fatalities, 13 are incorrectly reported based on the definition specified by the National Highway Traffic Safety Administration (NHTSA) (Noland et al. 2017). These include intentional homicides, incidents not on a public traffic way such as on private land, and one workplace accident. At least, nine of these incidents do not involve a pedestrian, if we assume that pedestrians are traveling on foot from one location to another. Another 22 incidents, all of which are within NHTSA’s definition, do not involve pedestrians, but merely people not in a vehicle who are struck and killed. Most of these are cases where a driver was standing next to a vehicle or was walking away from a disabled vehicle along a high-speed road. As their primary mode of travel was a motor vehicle, they are more representative of the risk of driving and not the risk of being a pedestrian. Thus, over 20% of the total reported pedestrian fatalities in New Jersey for 2012 are not really pedestrians engaged in purposeful travel from one place to another (Noland et al. 2017).

Another issue is the inability to obtain raw data records from many states. While the federal government maintains the Fatality Analysis Reporting System (FARS), which is a publicly accessible dataset, injury data is not centrally collected and is generally unavailable. We explored obtaining data to assess the openness of state agencies with sharing this data for both analytical purposes and their willingness for us to make it easily accessible via online mapping tools. Some states are very open with their data repositories, and others have flatly refused to make their data available citing liability concerns; that is, they fear that should a crash occur then the data will be used to sue them. This shows a lack of agency accountability; one objective of open data is to make state agencies accountable to their constituencies.

With these data limitations in mind, some analysis of both nationwide data and New Jersey state data is presented in the next section.

9.6 What Policies Reduce Fatal and Injury Crashes?

Developed countries have seen enormous drops in fatalities associated with traffic crashes over the last 40 years (for the USA, see Fig. 9.3). This has occurred despite increases in vehicle usage and total populations. Recent research I have conducted has sought to identify some of the major policies associated with these trends. Of key interest is the role that the road network plays, especially given the large investment in trying to make roads safer.

Fig. 9.3

(source NHTSA)

Total traffic fatalities in the USA, 1967–2018

Work that I conducted about 18 years ago (Noland 2003) sought to examine changes in the road network while controlling for other policies enacted by states. Using a cross-sectional time-series methodology of state-level data, it was found that most of the reduction (from 1984 to 1997) was associated with increased safety-belt use, reduced alcohol consumption, and better medical technology. Changes in demographics also played a role, as the fraction of the population below the age of 25 decreased, which is typically a group at higher risk of crashes. Various road network features were found to have positive associations with fatalities and injuries, such as increases in arterial and collector roads, and overall lane mileage. While effects were weak, there was evidence that larger lane widths (of arterials and collectors) are associated with more fatalities and injuries.

An updated analysis (Noland and Zhou 2017) evaluates a broader set of policies, including those initiated in the prior 15 years. These include the implementation of graduated licensing policies, more motorcycle helmet laws, new laws that regulate mobile phone usage, reductions in alcohol consumption, and improved medical technology (as measured by a proxy variable). The economic climate has also had an impact, with the 2008 financial crisis and recession associated with drops in total fatalities, something seen in many other studies. An increase in the fraction of collector roads was associated with fewer fatalities, i.e., more arterials likely increase fatalities.

Those policies that tend to increase the cost of mobility, i.e., regulations on driver behavior such as motorcycle helmet requirements, mobile phone laws, and graduated licensing laws, all are effective. Those that reduce the cost of mobility, such as adding more arterial roads, tend to increase fatalities. Improvements in medical technology tend to reduce the likelihood of a fatality so while this reduces the cost of mobility, there is still a beneficial impact. This is consistent with what we would expect from behavioral adaptations.

The record on pedestrian fatalities has been mixed, with a drop since about 1973, as seen in Fig. 9.4. Data prior to this time period was not collected by NHTSA, and there is a large discontinuity between 1972 and 1973, but there was likely a large reduction after the reported peak in the early 1930s. Since about 2003, however, there has been an increase in total pedestrian fatalities from a low of 4109 to 5489 in 2018.

Fig. 9.4

Pedestrian fatalities in the USA, 1927–2018 (sources National Safety Council, 1927–1972; NHTSA, 1973–2018)

New Jersey has had a fairly constant number of pedestrian fatalities since 1994 as shown in Fig. 9.5, and it is not possible to ascertain a trend. New Jersey has a relatively low incidence of traffic fatalities, but the proportion of those that are pedestrians is one of the highest in the nation (about 20%). This is largely because the state is densely populated, so exposure levels are higher. In Fig. 9.6, one can see the relative distribution of pedestrian casualties throughout the state; these roughly track the major population centers in the north and south of the state.

Fig. 9.5

(source NHTSA, Traffic Safety Facts and FARS data)

New Jersey pedestrian deaths, 1993 to 2018

Fig. 9.6

(source Plan4Safety, Rutgers Center for Advanced Infrastructure and Transportation; Google Maps)

Geo-coded pedestrian crashes in New Jersey, 2003–2013, representing about 35% of total pedestrian crashes

Analysis we conducted has examined both the probability of pedestrian casualties occurring throughout the state and a more detailed analysis of associations between road and pedestrian infrastructure and the level of severity of pedestrian crashes. The crash frequency analysis used spatial data from 2003 to 2008 to examine factors associated with pedestrian casualties (Noland et al. 2013). In general, results show that lower-income areas tend to have more casualties and areas with lower household vehicle ownership likewise have more casualties. These would be areas where people are more dependent on walking to engage in economic activities so exposure levels are likely higher. Alternatively, casualty rates are higher in areas with lower population density where streets usually have higher speed limits and fewer safe areas for pedestrians to walk. A greater density of major highways, excluding controlled-access highways, is also associated with more pedestrian casualties (Noland et al. 2013).

To examine the relative severity of pedestrian casualties, we analyzed the road and pedestrian infrastructure for over 2500 crashes using imagery from Google Street View (Hanson et al. 2013). The features examined included the number of lanes, speed limits, presence of sidewalks and whether they had buffers along the street, crosswalk types and presence of medians. The results suggest that casualties are less severe when there are reduced speed limits, fewer lanes of traffic, and sidewalks with buffers (Hanson et al. 2013).

In general, these results suggest that a major source of pedestrian fatalities is large high-speed roads without adequate pedestrian infrastructure. These may also be more likely to cut through lower-income neighborhoods, partially explaining the frequency of crashes in those areas. In short, roads such as those in Fig. 9.7 are not safe for pedestrians, while the one pictured in Fig. 9.8 is relatively safe. All the images were the site of a pedestrian crash. The former were fatalities while the latter was a minor injury.

Fig. 9.7

(source Google Street View)

High-speed arterials with no pedestrian infrastructure, (left image) US 130, Cinnaminson, Burlington County, NJ, and (right image) Bergen Boulevard (NJ 63), in Palisades Park Borough, Bergen County

Fig. 9.8

(source Google Street View)

Low-speed two-lane street with buffered sidewalks, CR 655, Maplewood, Essex County, NJ

9.7 Solutions: Sharing the Street

Many cities in the USA and throughout the world are now recalibrating the balance of providing unimpeded traffic flow versus providing safety for pedestrians. These concepts range from traffic calming to slow traffic, mainly on residential streets, to shared space concepts, to reallocation of road space to reduce lanes for vehicles and provide more space for pedestrians.

Times Square in New York City, which is the heart of the theater district, was bisected by a major arterial road, Broadway. In 2009, Broadway was closed to traffic and the space reallocated to pedestrians (Fig. 9.9). The result has been a substantial increase in pedestrian activity and a much-enhanced environment for pedestrians, so much so that space is limited and some are complaining of too many pedestrians (Bagli 2015). If too many pedestrians are a problem, then one solution is to close additional streets that still traverse the square.

Fig. 9.9

(source NYC DOT)

Times Square, New York City, before and after pedestrianization

In London, a good example of a shared space concept was recently completed in South Kensington along Exhibition Road. This street runs from Hyde Park in the north down to the South Kensington Underground Station, passing by a major university and three large museums that attract substantial pedestrian traffic. During peak periods, the sidewalks were previously overcrowded and the vehicles on the street tended to speed through the area, making crossing dangerous. The concept of shared space is to send a message to motorists that they will share the road with pedestrians; this is done by eliminating curbs and putting a textured pavement on the street. In this case, the speed limit was lowered from 30 to 20 mph, which some might argue is still too high. The images in Figs. 9.10 and 9.11 show before and after images of Exhibition Road and clearly show how the capacity for pedestrians has been expanded.

Fig. 9.10

(source Royal Borough of Kensington and Chelsea)

Exhibition Road, South Kensington, London, before shared space

Fig. 9.11

(source author)

Shared space, Exhibition Road, South Kensington, London

Another concept being employed in the USA is a Complete Streets policy. This policy aims to reconfigure existing street design so that all road users are accommodated, pedestrians, cyclists, motorists, and transit. One implementation of this is the concept of a “road diet,” which involves reducing the number of lanes for streets that were over-designed for vehicle capacity. This commonly involves taking a road with two lanes for traffic in each direction and converting it to one lane in each direction with a shared turning lane separating the traffic lanes. Normally, there is then additional road space to also add a bicycle lane on either side of the street, although not all implementations include this.

We conducted research to evaluate the costs and benefits of implementing a road diet along Livingston Avenue, a 1.5 mile arterial corridor in New Brunswick, New Jersey (Noland et al. 2015). This street runs from a major intercity arterial to the center of New Brunswick, traversing mainly a residential neighborhood but with some commercial activity and several schools along its length. Figure 9.12 shows the street as it is currently configured while Fig. 9.13 shows an overlay image of what a road diet would look like.

Fig. 9.12

(source Noland et al. 2015)

Livingston Avenue as it is currently configured

Fig. 9.13

(source Noland et al. 2015)

Photo simulation of Livingston Avenue with a road diet

The costs associated with the road diet mainly consist of any additional travel time delay associated with reducing the capacity and subsequent vehicle throughput, as well as the construction costs (mostly restriping the pavement) associated with the conversion. The benefits are the expected reductions in vehicle crashes. There are also potential benefits of improving pedestrian mobility, although we did not attempt to assess these.

To estimate the travel delay, we ran several simulations using VISSIM micro-simulation software (Noland et al. 2015). The value of travel time applied to the delay was based on formal guidance provided by the US DOT (Trottenberg and Belenky 2011), equivalent to 50% of the median income of $12.75 per hour; for business travel, it is 100% of the median income or $25.50 per hour. Values were indexed to 2014. To estimate the cost of crashes, estimates of the value of statistical life were used, again based on US DOT guidance (Trottenberg and Rivkin 2013). The 2014 value ranges from $5,311,875 to $13,177,537, with a mean of $9,295,782. As most crashes do not involve a fatality, factors are applied based on the level of severity of a crash as shown in Table 9.3. The number of crashes per year is about 38, on average with 17% involving pedestrians and 43% involving an injury. As we do not know precisely what the reduction in crashes will be, we assumed a 19% reduction based on a review of the crash reduction potential of similar road diet conversions (Thomas 2013).

Table 9.3 Relative disutility factors by injury severity level (AIS)

Given the uncertainties about some of our assumptions, we conducted a detailed scenario analysis over a 20-year time frame. In all cases, the net present value of the road diet conversion was overwhelmingly positive. Benefits ranged from about $8 million to over $40 million.

Most of the political debate surrounding road diets involves a fear of creating congestion or reducing the level of service of the street. This was the case in New Brunswick as there was a desire to complete the study well before an upcoming election. However, shortly after the study was completed, three children were hit by a vehicle and one suffered serious injuries. After political protests over the safety of the street, the city began more detailed engineering work and committed to doing the conversion. Some initial restriping was done in front of schools along with a few blocks of the street, shortly after the crash. A photo is shown in Fig. 9.14. Work began on the project in early 2020, some six years after the decision to do so.⁴

Fig. 9.14

(source author)

Restriping of Livingston Avenue in May 2014

9.8 Conclusions

In this chapter, I have reviewed the historical conflicts over road space and their resolution in favor of the motorcar in both Great Britain and the USA. While these conflicts were suppressed for many years, they have recently reemerged, recognizing that engineering guidelines on how to build roads ignored the pedestrian and damaged the fabric of many cities. The viewpoint that insists on reducing traffic congestion and facilitating traffic flow at any cost has been challenged.

From a research perspective, it is important to continue to evaluate the relative costs and benefits of traffic flow versus pedestrian safety. Benefits of pedestrianization can be more difficult to measure than travel time savings for vehicles. While safety improvements are one measure, other quality of life improvements are difficult to quantify. Safety data systems also need to be up to the task, they clearly are not in the USA, and developing countries often have even less reliable data systems. Making this data publicly available, both for researchers and to enforce government accountability, is crucial.

What are the lessons for developing countries, especially those that are rapidly motorizing? While motorization can improve mobility and economic linkages, it must be managed in such a way that the city is not destroyed as a place where pedestrian activity can thrive. Large high-speed arterial roads are chasms that pedestrians cannot cross and damage the linkages between neighborhoods. Traffic engineers and transport planners need to be thoughtful about following engineering guidance documents on how to design roads and improve safety. The locational context of where road infrastructure is placed must not be ignored. The main lesson is to find the right balance, and many cities have gone too far in catering only to motorized traffic at the expense of pedestrians.

There are growing examples throughout the world of successful reallocation of space from vehicles to pedestrians. These increase the vibrancy of neighborhoods and reduce many of the negative costs associated with an overreliance on motorized transport. A good example in India is Raaghiri Day.⁵ This is a weekly event where selected streets are shut down to traffic and opened to all for entertainment and recreation. This is part of the Open Streets movement that seeks to reclaim streets for all users. Originating in Bogota, Columbia, with Cyclovia, these have proliferated throughout the world.⁶ These serve to educate the public about how streets can be used for other purposes and hopefully will lead to broader institutional changes.