Automated Continuous App-Based Traffic Alerts Reduced Uninformed Drivers by 79.45 Percent on a Slovenian Motorway.
A Slovenian Field Evaluation Compared Manual and Automated Traffic Warnings Delivered Through Deployed Systems of Intelligent Transportation Systems Overhead Signs and a Cooperative Mobile App.
Slovenia
The Impact of Time Delays in Traffic Information Transmission Using ITS and C-ITS Systems: A Case-Study on a Motorway Section Between Two Tunnels
Summary Information
Timely traffic information is critical for safe and efficient roadway traffic operations, particularly near tunnels where incidents can quickly lead to congestion and secondary crash risks. Intelligent Transportation Systems (ITS) and Cooperative Intelligent Transportation Systems (C-ITS) are typically used to detect traffic events, transmit warnings, and help drivers respond before they enter hazardous or restricted roadway sections. To measure effectiveness of such systems, this study evaluated how quickly traffic information was delivered to drivers on a Slovenian motorway segment on the A1 motorway. Specifically, the study compared two information channels: conventional ITS overhead sign structure installed along the roadway and the Promet+ mobile application, which serves as a C-ITS-based communication channel, using real-world traffic and system data from October 16, 2024.
METHODOLOGY
The study evaluated four traffic information transmission methods: (i) manual activation of ITS overhead sign, (ii) automated activation of ITS overhead signs, (iii) manual transmission to the Promet+ mobile application, and (iv) automated transmission to the Promet+ application. For the mobile application, two update settings were also tested: (i) continuous updating, where alerts were delivered immediately after a system trigger, and (ii) periodic updating, where the application checked for new information every 60 seconds.
The analysis used real-world traffic volume and average speed data collected from an automatic traffic counter. The observation covered a 16-hour period, with results evaluated during the morning and afternoon peak hours. System performance was assessed using two main measures: the time delay required to deliver traffic warnings and the estimated number of drivers who were not informed in time under each notification scenario. This allowed the study to compare the timeliness and coverage of conventional ITS overhead signs and the C-ITS-based Promet+ mobile application across different modalities.
FINDINGS
-
Automating incident notification reduced the time from incident detection to driver notification from 34 to 25 seconds for roadside ITS signs and from 27 to 18 seconds for Promet+ mobile app alerts, compared with manual activation.
-
Automated alerts delivered through the Promet+ mobile app provided the fastest notification, reaching drivers 18 seconds after incident detection, while manually activated roadside ITS signs had the longest notification delay (34 seconds).
-
Combining automated activation with continuous Promet+ app updates minimized the number of drivers who were not warned before reaching the incident, reducing the total to 15 drivers during the morning peak and 8 during the afternoon peak. This represented a 79.45% reduction in uninformed drivers compared with relying on only the first roadside overhead sign.
-
Expanding automated ITS sign activation from the first overhead sign to all three overhead signs reduced the number of drivers who were not warned in time during the morning peak from 73 to 26 drivers, demonstrating that broader roadside message coverage substantially improved driver notification.
