In Depth Analysis of the Speed Limits in the Road Network of Lazio Region

The speed limits are a critical aspect in terms of safety perspective, representing one of the most effective tools for alerting road users even to potentially imperceptible criticalities. Therefore, speed limits influence the behavior of individual road users in driving and in promptly noticing any dangerous situation. Furthermore, in terms of safety, it affects the interaction among different vehicles: heterogeneous speeds, due, for example, to some users adhering to the limits and others assuming different speeds, usually result in an increase of road accidents and critical issues in carrying out safe and smooth driving behavior. This study concerns an in-depth speed limits analysis carried out in the ASTRAL road network in Lazio region, Italy. The analysis concerns the sections outside the urban areas for a total extension of the road network analyzed of about 1,000 km including roads with single and dual carriageways. An innovative, robust and data-driven process for reviewing speed limits is proposed, based on the data provided both by a High-Performance Vehicle regarding current speed limits signs and by Floating Car Data for speed data. Additional information has been integrated to make a systematic process of analysis, derived from the use of multiple factors and aspects as road safety historical data, urban areas limits, boundary conditions, etc. The results of the study permit to carry out a) the development of guidelines in approaching the design of vertical road signs related to speed limits and b) the identification of specific issues related to the speed limits signs (data to process, numerousness and location of signs, presence of intersections, coordination with other roads and coordination with other road signs, etc.).