In the paper, crash prediction models for estimating the safety of the rural motorways are presented. Separate models were developed for total crashes and severe (fatal plus all injury) crashes. Generalized linear modeling techniques were used to fit the models, and a negative binomial distribution error structure was assumed. The study made use of a sample of 2,245 crashes (728 severe crashes) that occurred in the period 2001–2005 in the Motorway A16 Naples-Canosa in Italy. Many characteristics of the motorway are sub-standard. It allowed to investigate a wide spectrum of geometric configurations. The models were developed by the stepwise forward procedure using explanatory variables related to: traffic volume and composition, horizontal alignment, vertical alignment, design consistency, sight distance, roadside context, cross-section, speed limits, and interchange ramps. The decision on whether or not to keep a variable in the model was based on two criteria. The first was whether the t-ratio of the variable’s estimated coefficient is significant at the 5% level. The second criterion is based on the improvement of the goodness of fit measures of the model that includes that variable. Goodness of fit measures were theparameter R2α and the Akaike’s Information Criterion. All the parameters have a logical and expected sign. Most important result is that design consistency measures significantly affect road safety not only on two-lane rural highways but also on motorways

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This paper focuses on developing a method for road managers to assess the sideways-force coefficient (SFC) in porous asphalt with low-cost standard tests. SFC can be used as a component in road surface condition surveys and asset management decisions. A standard piece of equipment for determining SFC is the sideways-force coefficient routine investigation machine (SCRIM), which can be truck or trailer mounted. This equipment is often beyond the budget of most small, low-volume road agencies. An empirical model for the indirect estimation of SFC for porous road surfaces was developed as a result of this study. With handheld equipment—the portable skid resistance tester [to derive the British pendulum number (BPN)] and the sand patch method [height in sand (HS) test]—a correlation of these test results can be made, and a reasonable approximation to SFC with the use of the SCRIM method can be attained. BPN, the unit of measurement of the skid tester, is a representation of the microroughness of the wearing surface, and the sand patch method (HS test) results yield the macroroughness of the pavement. The study was conducted over 20-km segments of low-volume roadway in southern Italy. The initial results are promising, with a maximum percentage of error of less than 15.2%. Further study is needed to adapt the model to other road surface conditions.

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