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Safety at the heart of urban road concession design Américo Vespucio Oriente ~ Santiago, Chile

Designs for the Américo Vespucio Oriente (AVO 1) concession in Santiago have been assessed using the iRAP Star Rating Methodology prior to its commission in 2022.

One of the largest infrastructure projects in Latin America, the concession will move traffic to a free flow underground road network, providing an innovative solution to high traffic saturation, poor flow and north-south connectivity in the city.

It will reduce pollution, cut travel times from 40 minutes to 10 and improve pedestrian and bicycle mobility.

In the Metropolitan Region of Santiago, the AVO I Concession Project extends for 9.1 kilometres through 6 suburbs from Avda. El Salto in the north to Avda. Príncipe de Gales in the south. AVO I and AVO II (Príncipe de Gales – Los Presidentes) are the missing links in the Américo Vespucio road ring that encircles much of the greater metropolitan area.

As part of the AVO project, the Vespucio Park, which extends from Padre Román in the Vitacura district to Avda. Príncipe de Gales in La Reina district, will see its area of green space increased by 15,000 m2, improving pedestrian and bicycle mobility within the park, improving connections for pedestrians and bicyclists with nearby green spaces, including Parque Metropolitano and Bosque Santiago, and also improving connections to the wider bicycle path network in Santiago.

The mainline cross-section of the concession is comprised of 3 free flow lanes per carriageway, and the project is divided 2 main sectors:

Sector 1

Extends from the Avenida El Salto to the Centennial Bridge, includes the construction of a main overpass and a secondary overpass, a 3-lane bored tunnel under Cerro San Cristóbal and another under the Mapocho River, as well as improvements to the existing surface road on the descent from La Pirámide.

Sector 2

Extends from the Centennial Bridge in the north to Avenida Príncipe de Gales in the south and is comprised of dual 3-lane carriageway tunnels which will be constructed using both bored and cut and cover techniques.

To ensure the concession is engineered to provide adequate safety for its users, the Sociedad Concesionaria Vespucio Oriente SA (SCAVO) engaged the International Road Assessment Programme (iRAP) to Star Rate 19.3km of proposed designs to assess the level of safety and recommend a Safer Roads Investment Plan with the goal of achieving a minimum 3-star or better safety standard, prior to construction.

iRAP Project Manager Morgan Fletcher said,

"Engineering safety at the design phase is a smart investment of time and money, and essential for reducing road trauma.

“Being able to identify high-risk road sections and alter the design to improve safety before construction translates to reduced crashes, fatalities and injuries. It can be incredibly expensive, and sometimes cost-prohibitive to change road infrastructure once it’s built but a tweak of the design is very easy. The client can immediately see how many lives a change will save and prioritise investment accordingly,” Mr Fletcher said.

“Where a design change isn’t logistically feasible, reducing speeds is an effective solution to improving safety,” he added.

The iRAP Star Rating considers characteristics of the road infrastructure and how they directly influence the probability and severity of traffic crashes. A 1-star road is the least safe, whilst a 5-star road is the safest.

The iRAP Star Rating of the AVO I concession design provided a simple and objective measure of the level of road safety ‘built in’ to the design.

The results for the principal road user group for the AVO I concession - vehicle occupants - are detailed below. Pedestrians and cyclists were not considered in the analysis based on the restricted access of the infrastructure, and based on AVO modelling, motorcycle flows are expected to be minimal and are therefore not shown.

Existing Design

This map shows the Star Rating results of the existing Base Design of the Américo Vespucio Oriente Highway Project, El Salto-Príncipe de Gales Stretch (AVO I), for vehicle occupants.

It is based on the Star Rating colour bands following where 3-star is the minimum Global Target for road infrastructure safety:

Preliminary results showed that for vehicle occupants 100% of the assessed road network obtained the recommended target of 3-star or better.

Improved Design

The iRAP assessment considered more than 90 proven safety treatments to generate a Safer Road Investment Plan (SRIP) to improve the design's Star Rating and recommend design improvements to save lives.

Two scenarios were provided for consideration:

SCENARIO 1: INFRASTRUCTURE IMPROVEMENTS

The AVO I Safer Road Investment Plan showed an investment of CLP 178.6 million (USD$220,000) to install 13.9km of shoulder rumble strips on high-risk sections would:

Avoid around 29 deaths and serious injuries over the next 20 years, with an overall cost-benefit ratio of $14 for every $1 spent.

Image taken from ViDA showing recommended location of rumble strips at the roadside. Source https://www.vida.org

The table below shows the Star Rating shift in the before and after improvements design:

Including shoulder rumble strips would result in almost 60% of the assessed network achieving a rating of 4- and 5-stars.

For Vehicle Occupants, the comparison of the road length rating 3-star or better between the base design and the improved Scenario 1 design, shows no apparent change; however, analysing the change in road length rated 4-star or better shows an improvement from 42% to 59.6% between the base design and the improved design incorporating recommended infrastructure improvements .

SCENARIO 2: IMPLEMENTATION OF SPEED CONTROL MEASURES

Due to the particular characteristics of the project, in which sections are present in bored tunnel, cut and cover tunnel and overpass, the costs related to implementing many potential safety measures that require a wider road footprint would be exceedingly high.

Operating speeds at high-risk sections could however be controlled in such a way to decrease risk and improve the Star Rating of the entire corridor without adding cost. Enforcing speed limits and particularly focussing on sharp curves where present would eliminate higher risk 2-star road sections.

Based on modelling, in the speed management scenario, 100% of the assessed length would achieve a 4-star or better rating for vehicle occupants:

All of the portion of the network rated 3-star now improves to 4- and 5-star safety
Analysing the change in road length rated 4-star or better shows an improvement from 42% to 100% between the base design and the base design plus speed management measures.

The change in risk scores for vehicle occupants can be depicted graphically:

In a comparison of the Base Design versus the Base Design plus Speed Management, the design achieves 4- and 5-star safety, eliminating the previous 58% of the design rated at a 3-star level of safety.

Mr Fletcher said speed is a key element of the Safe System and the probability of being involved in a serious or fatal crash increases considerably even with small increases in vehicle speeds.

“Research suggests just a 5% increase in average speed leads to a 20% increase in the likelihood of injury in the event of a crash, and a 20% increase in the probability of a fatality.

“It is important that drivers adopt a safe speed for the road environment, the traffic mix and the fleet involved. Speed limits must be appropriate for the road design.

“Given the difficulty of implementing improvements in the AVO I underground, speed control is the best alternative to guarantee a 3-star or better journey for its road users,” Mr Fletcher said.

SCAVO General Manager Luis Eusebio said AVO I is one of the most important public infrastructure initiatives underway in the country.

“Not only is it large in magnitude, it also combines a series of construction methods: overpass, cut and cover tunnel and bored tunnel.

“Protecting road users is a priority and achieving 3-star or better allows us to have a benchmark against which to measure performance on our concessions in relation to international safety standards," he said.

“Having this evidence base to measure the safety of the existing design and investment plan and quantify the cost of recommended improvements allows us to plan the implementation of countermeasure recommendations to provide safe travel for our users”, Mr Eusebio added.

According to Chile's National Traffic Safety Commission (Conaset), 1,479 road deaths were reported in the country in 2020. The United Nations Sustainable Development Goals seek to halve the number of deaths worldwide, in part through the adoption and application of the iRAP Star Rating methodology.

Achieving UN Targets 3 and 4 for >75% of travel on 3-star or better roads for all road users by 2030 in Chile stands to save nearly 500 people per year with an economic benefit of USD$27.3 billion - a $7 benefit for every $1 spent.

Source: https://www.vaccinesforroads.org/irap-big-data-tool/

FOR MORE INFORMATION:

How to Star Rate a Road Design: https://irap.org/star-rating-for-designs/

AVO I progress news: https://www.scavo.cl/sala-de-prensa/

Full AVO I modelling videos: https://www.scavo.cl/sala-de-prensa/

For media enquiries: Judy Williams, Global Programme and Communications Manager, iRAP on email judy.williams@irap.org

Download a print friendly version of this article, here.

ABOUT STAR RATING FOR DESIGNS:

Star Rating for Designs empower designers to assess the road safety of a design and improve its safety star rating before the road is constructed, thus saving lives and preventing serious injury from the outset. By providing a means of objectively measuring the impact on risk of various design iterations, the Star Rating design process helps to harness the potential of designers to find creative solutions to challenging safety problems. For governments and development banks, the process opens the opportunity to set performance-based targets for vehicle occupants, motorcyclists, pedestrians and bicyclists that not only improve safety but create a high level of transparency and accountability. The process has been successfully used in countries such as Australia, New Zealand, Moldova, Qatar and India, in conjunction with existing mechanisms such as Road Safety Audits and highway design standards. iRAP has developed a web-based app, training and standard specifications to undertake a Star Rating of a Design that can be included in your project and a trusted network of trained Design Star Rating suppliers around the world is also available.

ABOUT IRAP:

iRAP is a registered charity with the vision for a world free of high-risk roads. The charity is active in over 100 countries and works with governments, development banks, mobility clubs, research organisations and road safety NGOs to provide them with the free tools, systems and training to make their roads safer. iRAP’s Star Rating Methodology provides a simple and objective measure of the level of safety which is ‘built-in’ to the road for vehicle occupants, motorcyclists, bicyclists and pedestrians. A 1-star road is the least safe and a 5-star road is the safest. iRAP’s Vaccines for Roads is a valuable online resource unlocking the potential of the world’s largest road infrastructure safety database to explore the human and financial impact of road injury, how safe the world’s roads are and provide the Business Case for Safer Roads. The charity has influenced the safety of over USD$80 billion dollars of infrastructure investment, has Star Rated over 1.3 million kms of roads, Risk Mapped over 1.5 million kms of roads, trained over 22,000 people and accredited 155 suppliers globally. iRAP is the umbrella programme for regional road assessment programmes including EuroRAP, ChinaRAP, AusRAP, usRAP, KiwiRAP, IndiaRAP, BrazilRAP, South Africa RAP, ThaiRAP and MyRAP and is financially supported by the FIA Foundation, Global Road Safety Facility and FedEx.

ABOUT SCAVO:

ALEATICA SA, (ex OHL Concesiones SA) together with SACYR Concesiones Chile SpA formed the Sociedad Concesionaria Vespucio Oriente SA, the holding company for the execution of the contract for the “Américo Vespucio Oriente Concession, Av. El Salto - Príncipe de Gales Section. Américo Vespucio Oriente will extend 9.1 kilometers from Avda. El Salto to the Príncipe de Gales sector. The project is part of the Santiago Urban Transportation System improvement program promoted by the Government of Chile, through the Ministry of Public Works.