Unlike other pavement indices, the skid resistance, or friction, of bituminous pavements behaves differently. After the extension of a new layer, the friction increases as the bitumen film is removed and the aggregates are exposed. The aggregates are then polished by traffic, mainly by heavy vehicles, and the pavement reaches the seasonal phase, in which, if heavy traffic volume remains constant, the only variations are seasonal, with maximum values in winter and minimum values in summer. Nonetheless, in tunnels, as they are not exposed to climatic actions, the friction value is lower than outside. Therefore, the article evaluates the skid resistance decrease in tunnels compared to outdoor conditions. For this purpose, the skid resistance values in dual-carriageway tunnels in Gipuzkoa (Spain) were studied and compared with the values obtained 500 m before and after the tunnel. Overall, a 10% friction decrease was observed inside the tunnels. In winter, the decrease was 11%, while in summer it was 8%. In tunnels longer than 500 m, the decrease was greater (12%) than in tunnels shorter than 500 m (9% and 7%). This analysis contributes to a better knowledge of the available friction inside a tunnel and to the better management of road safety.

Skid resistance, or friction, on a road surface is a critical parameter in functional highway assessments, given its direct relationships with safety and accident frequency. Therefore, road administrations must collect friction data across their road networks to ensure safe roads for users. In addition, having a predictive model of skid resistance for each road section is essential for an efficient pavement management system (PMS). Traditionally, road authorities disregard rural roads, since they are more focused on freeways and traffic-intense roads. This study develops a model for predicting minimum-available skid resistance, which occurs in summer, measured using the Sideway-force Coefficient Routine Investigation Machine (SCRIM), on bituminous pavements in the single-carriageway road network of the Province of Gipuzkoa, Spain. To this end, traffic volume data available in the PMS of the Provincial Council of Gipuzkoa, such as the annual average daily traffic (AADT) and the AADT of heavy vehicles (AADT.HV), were uniquely used to forecast skid-resistance values collected in summer. Additionally, a methodology for eliminating outliers is proposed. Despite the simplicity of the model, which does not include information about the materials at the surface layer, a coefficient of determination (R²) of 0.439 was achieved. This model can help road authorities identify the roads for which lower skid-resistance values are most likely to occur, allowing them to focus their attention and efforts on these roads, which are key infrastructure in rural areas.

Roadwork zones are high-risk environments where sudden geometric changes, narrowed lanes, and driver unfamiliarity frequently lead to inappropriate speeds. Ensuring safe vehicle speeds in roadwork zones remains a priority due to drivers’ limited perception of risk and frequent non-compliance with temporary limits. This study evaluates the effectiveness of a speed monitoring display (SMD) installed in a nighttime, four-day motorway roadwork site involving a temporary median crossing, where traffic was diverted through a single lane and a chicane-type re-entry. Speed data were collected at two points, 100 and 50 m before the median crossing, labelled as P1 and P2, respectively, during two phases: with standard work zone signage only (Phase 1) and with an SMD added (Phase 2). Results show statistically significant reductions in mean speed after SMD installation at both measurement points, including decreases of 7.09 km/h at P1 and 4.69 km/h at P2, with a greater reduction among heavy vehicles. The percentage of speeding vehicles fell from 95.4% to 81.9% upstream and from 63.4% to 35.7% near the chicane, indicating improved compliance in the most critical section (P2). These findings demonstrate that SMDs can effectively reduce speeds and variability even in very short-term work zones, supporting their integration as low-cost safety measures.