Lorenzo Domenichini

Transferability of the Highway Safety Manual Freeway Model to the Italian Motorway Network

The currently available release of the AASHTO Highway Safety Manual (HSM) does not include a model for freeways and interchanges. NCHRP Project 17–45 has recently developed specific crash prediction models for this type of infrastructure. Key to making the HSM a standard for road owners and managers worldwide is the transferability of prediction models to different networks. An extensive study conducted on the primary Italian motorway network evaluated the potential issues in application of this methodology to a network characterized by environmental conditions, road characteristics, driver attitudes, and crash reporting systems different from those for which the HSM models were developed. The freeway network considered in this study, approximately 6,700 km long, was represented by 56 freeway sections characterized by an average length of about 12.5 km, covering 700 km of freeway distributed throughout Italy. Four calibration factors were obtained for freeway segments, according to crash severity and type, and two calibration factors were obtained for speed-change lanes, according to crash severity. The results show a good transferability of the analyzed models to the Italian network, especially the freeway models for fatal and injury crashes, although a tendency to underestimate locations of high crash frequency was observed. Some improvements could be made concerning variable calibration factors within the data sets or local calibrations for crash modification factors. Improved localization of the crash data on the Italian road network needs to be highlighted, mainly for speed-change lanes.

Influence of the lighting system on the driver's behavior in road tunnels: A driving simulator study

ABSTRACT The tunnel lighting system is an important factor affecting driving safety, but it also represents the most expensive operative cost of a tunnel. Conventional tunnel lighting systems have been progressively replaced by LED lighting systems. This technology is spreading fast because of its low energy consumption and the high durability combined with low maintenance requirement. Aim of this research was to assess, by means of driving simulator experimentation, the impact of the LED lighting system on traffic safety. The driver performance approaching inside and exiting LED lighted tunnels was analyzed and compared to the behavior maintained in tunnels illuminated with a traditional system, in normal and in critical conditions. Thirty-one young participants drove through two different virtual scenarios while data on their speed, lateral position, and reaction in front of a sudden obstacle in the carriageway were collected. A statistically significant difference was revealed as a function of the type of lighting; simulated LED lights often induced a better driving behavior under some aspects. The motorists were able to perceive in advance the critical situation and the consequent maneuvers were carried out in a more effective way. Moreover, drivers kept better their lateral trajectory control in transition areas.

Evaluation of the vehicle/safety barrier/sign support interaction by means of FEM simulations

This paper deals with the evaluation of the interaction between a safety barrier and a variable message sign (VMS) that is placed very close to the carriageways in order to reduce the length of the arm above the carriageways. The two issues addressed are the structural response of the VMS, in order to ensure that the structure will not fail under the impact of a heavy goods vehicle (HGV), and the effects of the secondary impact that occurs when the barrier or the vehicle hits the VMS structure. These issues have been analysed both in terms of overall performance of the barrier and of the resulting effects on the HGV itself. As a result, the minimum distance between the front of the barrier and the VMS support structure that will enable to have a performance fully compatible with the requirements of EN1317-2:2010 has been defined for a specific barrier/VMS system.

Rail Tunnel Risk Analysis: A Tool to Improve Rail Tunnel Design

A methodology to conduct an extended risk analysis in accordance with Italian law was applied to evaluate the effects of rail tunnel characteristics on the likelihood of passenger survival in case of a fire. The procedure allows one to calculate the heat and toxic gasses concentrations inside a tunnel due to a fire of different characteristics (in terms of heat release rate and heat release development time) and to calculate their diffusion and their effects on passengers. The likelihood of saving people and the number of expected deaths as a function of the distances covered by each passenger have been obtained from the application of the methodology. The variables considered in the performed study included the fire event characteristics, the number of available safety walkways in the tunnel, the train offered capacity, and the escape capabilities of people (consciousness and reaction times and evacuation procedures). The applied methodology has been proven highly useful as a design tool to identify the best design, construction, and management options to increase safety levels.