Road infrastructures are fundamental assets of all developed countries and road authorities have the obligation to guarantee their maintenance and development toward the preservation of the pavement structure and safety conditions. To address decision-making departments, many different road measures and methods have been developed and every year a big amount of data is collected by specific vehicles from almost the entire road network. Both structural and functional conditions are quantified; the first defines the degree of deterioration of the materials and layers used in the pavement structure while the second quantify the quality of the driving conditions. As it can be expected, these two conditions are not independent each other because when a road pavement is in poor quality also its functionality get compromised.  

In the recent years, road pavements have been classified also in relation to their environmental emissions. In fact, quality and type of road surface have an impact on the tire/pavement interaction and consequently on vehicles noise emissions and energy consumption.

One of the first standard parameter introduced to define the pavement quality was the International Roughness Index (IRI) that defines the longitudinal profile of the travelled wheel-path. The IRI, introduced by the World Bank, affects not only the ride quality but also the vehicles delay costs and in general accounts for both structural and functional pavement condition. The IRI is a filtered ratio of a standard vehicle’s accumulated suspension motion (in mm.) divided by the distance traveled by the vehicle during the measurement (km).

Another parameter used by road owners is the rutting depth. Ruts generally appear due to the wear and weak load bearing capacity of the road structure. If ruts have appeared due to one of those reasons then water run-off is hindered and aquaplaning may occur.  

Both IRI and Rut Depth development must be monitored to address optimal long-term maintenance strategy.

Other typical pavement distresses are cracks and potholes. As cracking becomes severe, the interconnected cracks create small chunks of pavement, which can be dislodged as vehicles drive over them. The remaining hole after the pavement chunk is dislodged is called a pothole. Due to the very fast development of these distress types and consequently hazard for the traffic, it would be very beneficial from the road owner prospective to have more frequent data acquisition. Nowadays these damages are quantified using expensive 3D cameras but it is expected that vibration and pressure sensors should be able to detect them.

Friction between tire and pavement is another fundamental road characteristic, which must be guaranteed by the road authorities. Friction has been quantified by the use of a standard tire and a test method that simulates the Anti-lock Braking System (ABS) of conventional cars on wet surface. Furthermore, the developed methodology has the limitation that has been validated and used only at speeds higher than 60 km/h. The interesting aspect in this case is that by having access to the data of a car breaking system it would be possible to measure the friction properties of a specific pavement.

Pavement noise emissions are related to respective surface and texture conditions. A Close Proximity Method (CPX) is used to evaluate the sound absorption properties of road surfaces. With regard to the impact of pavement conditions on fuel consumption, it has been established that road properties such unevenness and texture influence vehicles energy consumption. The Danish Road Directorate has been working in the recent years on implementing management solutions and maintenance strategies that could account for the energy efficiency of road pavements. 

In general, all significant road properties, used to make management strategies, have been defined thinking at the relative impact of a road characteristic on a vehicle. Furthermore, the standard tests used to quantify a specific road property are based on data that should be directly or indirectly measured by sensors installed on conventional modern cars.

If there are limitations due to traffic, road geometry, speed limit or budget, the pavement survey is performed by visual inspection. Nowadays most of the municipalities uses the visual inspection which might not always be objective and it is directly dependent on the experience of the person in charge.

It is relevant to highlight that road authorities use standard methods while most of the municipalities operates by using visual inspection. In both cases, an assessment of the pavements conditions of the respective network requires up to three years. This time frame between consecutive surveys over the same sections in some cases are too wide. Damages on the infrastructure and hazards for the users must be detected in time to optimize management strategies and guaranty safe roads.  


An alternative way to collect data on road conditions was recently developed within the project Crowd4Roads where accelerometers in mobile phones were used to quantify road roughness. In this case, data reliability, resolution and sensitivity might be limited by difference in cars, phone models, sensors sensitivity and phone location. LIRA, by using identical cars, eliminates these biases and uses data from all the car sensors delivering not only roughness but also others strategic road properties such as friction, texture, noise, cracked surface, potholes and rutting.