The upgrade of a dynamic fourth lane on the A4 highway in Italy relied on road construction company Del Bono SpA and Trimble technologies’ improved process management to enable crews to safely and quickly work on a complex, dangerous construction site.
Widening One of the Busiest Stretches of Road in Italy
The project involved the construction of a dynamic lane through the temporary use (for one direction of the road or both) of a fourth lane carved out of the emergency lane and redistribution to the traffic lanes of the A4. In the event of heavy traffic situations, thanks to the installation of signaling systems that dynamically indicate lane opening and speed to drivers, traffic backups on one of the busiest roads in Italy will be mitigated.
The work on the A4 Turin-Venice freeway extends 9.36 km through the urban center of Milan. The widening works are in progress, with gradual opening of the dynamic fourth lane (from 2022) starting from the northbound carriageway (Turin direction) for the Cormano junction — Certosa interconnection with the A8.
As part of the platform operations, quality control is highly emphasized, in addition to compliance with the characteristics expressed in the Special Specifications. Amplia Infrastructures SpA, in agreement with the Client Autostrade per l'Italia, deliberately sought the application of a technology that would allow the achievement of a high standard of comfort for users' driving, through a control for the rolling planes of the highway platform with technologies made available by Del Bono Group SpA and Trimble, specifically the Trimble® MX9 and Trimble® S7.
The Trimble S7 Autolock Total Station
Guaranteeing Timing, Accuracy & Quality of Work in an Extreme Construction Site
The project will be implemented without introducing any changes to the route, almost exclusively within the existing road bed, except for some local extensions to carry out the works aimed at achieving an adequate level of traffic safety: formation of new lay-bys for emergency parking, access for emergency vehicles, and for the installation of variable message signs.
In addition, additional ancillary works are planned, such as modifications and restoration of a part of sub-services related to the hydraulic network, overpasses and underpasses resurfacing.
Specifically, the activities planned at the construction site by Del Bono SpA are the scarification of the existing bottom according to the new project slopes, laying of asphalt mix, execution of reinforced concrete works, and complementary works, including the highway seat furnishings.
The challenges of this construction site make it one of the most complicated in Italy in the road sector and are mainly related to the execution of the works in coexistence with the constant flow of existing traffic: up to 180,000 vehicles per day in both directions with hourly peaks of about 6,000 vehicles per direction. And, there could be only a few night closures at limited hours to carry out the most important work.
Construction site space is also extremely confined, narrowing in one direction or the other down to a single lane. Restore levelness to the road section resulted in numerous detours and site variants performed during construction.
Digitization of Processes and 3D Technology in Road Construction Sites
To overcome the challenges the site presented, the need arose to create a digital model of the work, replicating reality as closely as possible in the recreated model to make it possible to highlight the interferences, minimize unknowns, and anticipate any design errors that might occur on the site.
In order to achieve a complete digitization of the work, the prep stages of surveying and design had to be carried out accurately and with state-of-the-art technologies: technologically advanced digital mobile mapping and topographic tools to obtain an accurate model, and consequently, an optimal paving job.
The Trimble MX9 3D mobile mapping system
With the objective of restoring flatness to the entire road trunk, in this context, it would not have been possible to use only 2D technologies (already present on the milling machines) but had to carry out variable milling through the use of 3D technologies.
In fact, to be able to give the flatness required by the project to the road surface with the normal 2D process, all the road roughness would have recurred when laying the finished road mat.
The only option would have been to "stake out" the entire site and direct the milling machines with the help of these reference stakes. This traditional mode would have resulted in a more complex site, lengthened the project time, increased the probability of error, used more resources (surveyors’ and site assistants’ time) and more materials, all at the expense of cost and safety.
Universal Total Station (UTS) technology, which consists of maximum-precision optical total stations (coupled with machine control technology installed on the cutter) is revolutionizing road construction operations.
Using the 3D millimeter system, guided by robotic stations, allows milling at varying thicknesses, obviating the problems. In this way, the milling machine does not "copy" the road course but is guided by an optimized 3D design to recreate the correct flatness.
This approach makes it possible to eliminate staking, reduce the number of personnel near the moving milling machine, work under complex traffic conditions, and help visibility during nighttime work: in general, it allows an overall benefit to the project and to the construction site in terms of safety and efficiency. At Del Bono SpA's construction site, technology has a major component for solving challenges.
Fabio Del Bono, Managing Director of Del Bono SpA, with important jobs all over Italy and 50 years of industry experience, has invested over time in technology: tools, machines equipped with 3D, and operator training allows a leap in quality and differentiation from competitors in order to manage even the most complex projects.
Trimble Business Center data processing software
Trimble Workflows & Tools to Support Quality, Difficulty of Processing
The 9 km-long construction site was built using Trimble's innovative MX9 mobile mapping technology. Classic mobile mapping would not have allowed satisfactory accuracy for this construction site, so the use of the MX9 allowed for dense and precise point clouds (under 0.5 cm).
To give even greater precision to the work done by the MX9, georeferenced and leveled cornerstones with DiNi 0.3 m/km precision are additionally performed.
These cornerstones, which are used to increase the absolute accuracy of the point cloud, are then also reused for the execution of machine control at which total stations are placed with reference to the same cornerstones. Having a good network of leveled cornerstones allows near absolute accuracy, close to mm, which is impossible to achieve with current GPS technologies on the market.
Accuracy in this type of work is essential because of compliance rules regarding the thicknesses and the cost of materials is very high, so lower costs and increased quality of workmanship are important for the company performing the work.
The survey of the existing road, prior to the work, and the sections where it was not possible to survey with MX9 due to obstructions or interferences, was performed with Trimble SPS930 total stations, which are used both for the topographic element and for the use associated with machine control.
The survey and project were then modeled in Trimble Business Center (TBC) software, from which the processed model and project was then exported to the cloud via Trimble WorksManager platform directly to the machines, operators, and topographers on site, on Trimble TSC3 Controller.
The 3D design was then exported to the SPS930 robotic total stations. The total stations, already referenced with the cornerstones, engaged the Trimble MT900 active prism mounted on the milling machine and guided it automatically thanks to the Trimble PCS 900 machine control system, ensuring variable thickness milling and the desired depth.
In addition to optimizing the removal of the required amount of material, the subsequent asphalting and compaction stages were also prepared by creating a completely smooth and uniform flat road without undulations or imperfections, making it possible to carry out the subsequent asphalt paving stage using classic 2D technologies.
Wirtgen milling machine equipped with the Trimble PCS 900 3D UTS system
The use of technology and the digitization of the construction site are key to revolutionizing work processes, addressing complex challenges, and being indispensable enablers for the continued success and development of businesses in the industry.
A properly paved road, with millimeter-precise flatness, benefits from a high quality of workmanship by being more sustainable, increasing durability, increasing material management precision, lowering maintenance costs, optimizing rational control and use of machines, lowering the risk of repeated interventions due to miscalculations or incorrect scheduling, and above all, ensuring the safety of those those working on the construction site and those who travel along the road.
This article was published in Strade & Autostrade, a magazine specializing in construction, maintenance, management of transportation networks, public works, and infrastructure. Read the article in Italian here.