Road Safety in Cities: Street Design and Traffic Management Solutions
We introduce to you a booklet that presents effective measures that reduce road traffic deaths and serious injuries in cities. The work of the booklet was carried out in the context of the Safer City Streets initiative of the International Transport Forum (ITF) and funded by the FIA Road Safety Grant Program, supported by the FIA Foundation.
Street design in cities worldwide has been focusing on private vehicles, ignoring the other road users. Streets are public spaces that should be redesigned to maximize safety and inclusiveness of all road users. People are losing their lives every minute in city traffic and cities worldwide are taking action to improve urban road safety and make their streets safer. There is no intervention that can achieve all the desired safety outcomes and the proposed interventions are costly and can’t fit all cities.
This booklet introduces measures for urban street design and traffic engineering, speed management and improved mobility options. It presents nine groups of measures that have proven effective in reducing road traffic deaths and serious injuries in cities, outlining experience and case studies from some of the cities that are implementing such measures successfully. The booklet also presents traffic management and signaling systems as parts of the improvements being made to infrastructure. It discusses each specific measure which briefly reviewed in terms of cost and effectiveness. The examples of the reported effectiveness of some road safety measures presented in this booklet depend on the local context in which they are implemented.
The booklet starts by referring to the Safe System Approach that focuses aims at reducing risks in all areas of a road safety system including behavior and the risks inherent in the design of the road network.
Measure 1: Allocation of protected space for walking and cycling
Pedestrians, cyclists and two-wheelers are considered as vulnerable road users who are at greater risk of road traffic deaths and injuries. They need more improved street design and protected infrastructure. The booklet proposes sidewalks and cycle tracks to separate and protect the vulnerable road users from motor vehicles. While cycle track provides a hard separation, a cycle lane is separated only by road markings such as solid white line. Light protection of cycle lanes is another cheap and quick measure that consists of physical objects placed alongside a cycle lane to give additional protection from motorized traffic. Road junctions are critical to cycling safety and should be a starting point for allocating space to cycling.
Fortaleza is a Brazilian city that has succeeded to make a radical improvement to pedestrian infrastructure when it implemented a “Lively Sidewalk” program that included the conversion of one traffic lane into an interim sidewalk extension. The number of pedestrians who were forced to walk between motor vehicles reduced by 92% and vehicle speed above 30 km/h and 40 km/h dropped by 65% and 84% respectively.
Introducing a cycle lane in the Camden district in the northwest of London was the first one in the United Kingdom to use light protection to protect cyclists from traffic. The bi-directional cycle track was replaced with cycling routes using light protection measures instead of curb separation. This reveals a 50% reduction in both the number of crashes involving cyclists and the severity of resulting injuries. The total number of people cycling increased by 70% and motor vehicle traffic levels and speeds dropped.
Measure 2: Speed Management
Speed management is one of the most effective urban road safety policies. A 1% increase in severe speed results in approximately a 2% increase in injury crash frequency, a 3% increase in severe crash frequency, and a 4% increase in fatal frequency. Engineering measures, such as road narrowings, speed humps, curb extensions and raised pedestrian crossings and junctions, exist in 30 km/h zones and they have to be designed carefully to fulfill their functions.
A speed management program was developed to improve the road environment and guarantee the safety of all road users. The speed limits were evaluated in relation to road function, infrastructure condition, land use and operational characteristics and an appropriate speed was determined for each road type. The interventions targeted the five corridors with the highest casualty rates, speed limit was lowered from 60 km/h to 50 km/h and speed cameras were installed to enforce compliance. Interventions then targeted ten corridors and resulted in saving 46 lives in 2019 which represents a 21% decrease in traffic fatalities compared to the three previous years.
Lisbon has implemented curb extensions that reduce the crossing distance for pedestrians and increase the curve radius on all corners slowing cornering speeds. The intervention has led to a traffic-calming effect, no increase in traffic congestion and pedestrians felt (+18%) safer and drivers were less (-14%) pressured to walk faster.
Measure 3: Roadside safety treatment
Safety barriers and guardrails at the roadside are designed to prevent pedestrians from walking into the road and to protect them from motor vehicles. The safety barriers can reduce the number of severe crashes and maintain road safety if they are well designed and installed. The safety barriers and guardrails are intended to reduce conflicts between pedestrians and drivers.
London has experience in removing pedestrian guard railings as they can become more of a barrier to access than an aid to safety. Transport for London has implemented a policy to remove sections of pedestrian railings along main roads where they are counter-productive. Removing the railings reduced the number of fatal and serious pedestrian collisions by 53%. Crashes for all road users reduced by 47% at junctions where barriers had been removed.
Measure 4: Traffic management
There are different approaches to manage traffic but it mainly depends on street design. Traffic management primarily aims to prevent conflicts between road users by managing traffic volume and speed. The traffic management measures include pedestrian streets, low-traffic neighborhoods and traffic-calming measures. These measure allow more for pedestrianized streets where pedestrians and cyclists benefit from improved air quality and reduced air pollution.
In Barcelona, the “superblock” model has been proved effective in reprioritizing access in central parts of the city giving priority to pedestrians and cyclists. In the neighborhoods where superblocks have been created, road safety has been improved in terms of reduction in the number of motor vehicles. Moreover, residents have reported better rest in a quieter, more comfortable and safer environment.
Lisbon where home-school trips are characterized by the use of cars; has also witnessed traffic reduction in school zones through an initiative promoting sustainable mobility and a change in habits for commuting from home to school. The initiative is part of a school-mobility program that limits motor vehicles access to zones around schools particularly at the beginning and end of the school day. The project started in December 2019 and was launched in two cities including raising-awareness campaign by the school community. A considerable reduction of motor vehicles in school zones has been observed since the beginning of the project leading to safer conditions for children to walk and cycle to school.
Measure 5: Improved mobility options
The mobility options are one of the fundamental action areas of the Safe System approach. The public transport is the safest and efficient mode of transport as people are less likely to drive their private vehicles under the influence of alcohol, drugs or medicine. Walking and cycling are among the mobility options that improve road safety and have health and environmental benefits. High-quality public transport, bus priority junctions and bus priority lanes in addition to pedestrian infrastructure for stops and stations can improve road safety.
The New York City implemented a pilot program on 14th Street with the goal of improving the bus service, and increasing safety. Within the pilot program, only buses, trucks and emergency vehicles may travel along 14th Street between 6 AM and 10 PM. The program includes new pedestrian space, painted curb extensions to shorten pedestrian crossings and bus boarding platforms. The successful pilot has led to reduction in injuries by 42%, bus travel times have increased by 24% and ridership by as much as 30%.
Measure 6: Junction treatment
Junctions are common locations where most crashes take place as different categories of road users cross paths. There are different treatments to junctions like channeling, converting junctions to roundabouts, staggered junctions, grade-separated junctions and redesigning junctions. Evaluations of the European Road Safety Decision Support System reported strong positive effects for left- and right-turn channellisation and the number of crashes reduced by 27% and 19%, respectively. Grade separation of interesting roads, the most effective measure for preventing collisions at junctions, has led to reduction of crashes between 15% and 45%. However, it is costly and has several negative effects unlike converting junctions that reduces crashes by 38% and daylighting and other sight-distance improvements that have been found to reduce the number of crashes by 12%.
The Brazilian city, Fortaleza has implemented a safe junctions program in 2017 and junctions were modified with highly visible paint markings to channel traffic, shorten pedestrian crossing distances and widen pavements with some light protection. The program has been proven effective showing a reduction of 53% in the total number of crashes and a reduction of 60% and 48% for crashes involving injury and property damage.
In New York City, Turn Calming program was implemented in December 2020 with several types of treatment applied to redesign the junctions. The implementation of the program has led to a reduction in pedestrian injuries by 20%. Additionally, average left-turn speeds have decreased by 53% and average right-turn speeds have decreased by 34%.
Measure 7: Hot spot identification and treatment
Hot spots are high-risk locations where injury risk should be addressed as a matter of priority. Data reveals the accumulation of injuries and crashes caused by recurring factors such as road layout, road surface condition or vehicle manoeuvres. Mapping of hot spots can be identified using various tools and techniques as a proactive manner to prevent causalities before they happen.
A hot spot identification project was developed in Washington State with the city’s network of 360degree. High-definition traffic cameras have been installed at 40 intersections and video feeds were analyzed to collect data on traffic volumes, road user speeds, and near-crash traffic conflict indicators. The project was based on video monitoring, video analytics to diagnose specific issues in particular sites, select, implement improvements, and evaluate outcomes.
Measure 8: Improving road surfaces
Road surface is an important part of the street design that needs regular maintenance for durability in difficult weather environments. The regular maintenance of road surface is essential to the safety of all road users and extends the lifetime of pavements and should include maintenance of road markings and signage.
Dublin city has witnessed improvements in the road surface for cyclists. The improvements started with collecting data on speed, dwell time, collisions and near-miss events. The collected data allowed planners and engineers to improve the infrastructure that was found challenging to cyclists. The information gathered was also used to plan the development of Dublin’s most recent cycle infrastructure improvements.
Measure 9: Traffic signaling and intelligent transport systems
Technology plays an important role in increasing road safety through the innovative solutions of traffic signaling, traffic surveillance and control systems. For instance, timing and configuration of traffic lights are important for pedestrians’ safety. There is also vehicle-to-vehicle communication and vehicle-to-infrastructure that are important for emergency braking warning, distance sensing, improper driving detection and other systems. An Intelligent Speed Assistance was introduced in the EU from 2022 to regulate speeds and reduce the exposure of road users to crash kills. Studies show that improved traffic signal timing reduces the risk of pedestrian-vehicle crashes by 60%. Traffic signal installation at uncontrolled junctions can also reduce collisions by 29%.
In New York City, left turns account for more than twice as many pedestrian and cyclist fatalities as right turns, and over three times as many serious injuries and fatalities. The city has prioritized the treatment of left-turn pedestrian and cyclist injuries installing over Leading Pedestrian Intervals (LPIs) at priority intersections. A decline by 14% and 56% was found in left-turn pedestrian and cyclist injuries, kills and serious injuries respectively.