**6. Conclusions**

The goal of the research was to develop a methodology for the evaluation of the effects on safety and travel time of the rural Travel Time Information System. For this purpose, a flexible approach was used by calibrating ad hoc SPFs for road sections (national/regional roads and rural/suburban roads), intersections, and by assessing travel time for the same possible traffic scenarios.

The presented methods, through the estimation of the influence of traffic changes in the road network with the TTIS on safety and traffic performance, allowed us to evaluate the threshold values to be used in the the TTIS's control system. This is why, in order to efficiently operate, the TTIS has to be set with threshold values related not only to travel time but also for all the factors which can be directly influenced by the system based on the road network performance, categories, and exposure factors. Looking at the results, the use of the system makes it possible to improve the road safety that is particularly challenged when the network is made up of roads with different standards.

Therefore, given the different risks associated with different road categories, area types, intersection typologies, and the dynamic change in traffic volume (exposure factor) produced by rerouting, it is possible to estimate the TTIS effects on the road safety of the entire road network, by using the SPF models.

The problem of the analyzed system, and common to all ITSs, is that travel time is the only factor in the decision about rerouting traffic. Displayed messages should change from the value of travel time to the recommended way of choosing from multiple criteria, which should also consider road safety.

The ITS, while providing benefits for traffic operation, changes the overall safety performance of the road network. To avoid those effects, the system managemen<sup>t</sup> should be oriented toward more factors, finding a balance between traffic flow improvement and road safety. The methodology proposed in the paper, with a proper local calibration, can be readily used as a tool for practical applications.

Indirectly, the presented paper indicates the need to develop a navigation system with the selection of routes, taking into account the level of risk in road safety. The presented methodology can be useful to implement this approach in apps to inform drivers about risk. The changes in traffic volume observed by devices in the ITS can be used in the autocalibration procedures of SPFs. It can help to reduce the social cost of road network operation by reducing the number of crashes and victims.

**Author Contributions:** Conceptualization, M.K. and C.D.; methodology, M.K. and C.D.; formal analysis, C.D.; investigation, All; data curation, M.K. and S.P.; writing—original draft preparation, M.K. and S.P.; writing—review and editing, All; visualization, S.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
