Segmentation effect on developing safety performance functions for rural arterial roads in Egypt

Elagamy, Sania Reyad; El-Badawy, Sherif M.; Shwaly, Sayed A.; Zidan, Zaki M.; Shahdah, Usama Elrawy

doi:10.1007/s41062-020-00318-7

Cited by 3 publications

(7 citation statements)

References 29 publications

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“…The data of crash frequencies for each kilometer and traffic volumes along the rural sections were obtained from GARBLT for four years (2008 to 2011). This data can be found in [4]. It is worth noting that GARBLT classify the roads to agricultural and desert roads based on the roadside activities (i.e., land use).…”

Section: Data Descriptionmentioning

confidence: 99%

“…The desert roads are the roads on which the main roadside activity is desert, while the agricultural roads are the ones on which the main roadside activity is Agriculture. Four various segmentation approaches were used in this study [4]:…”

Section: Data Descriptionmentioning

confidence: 99%

“…The consecutive segments with curves or Uturns were merged into one segment, and the consecutive sections without curves or U-turns were merged into one segment. Four various segmentation approaches were used in this study [4]:…”

Section: Data Descriptionmentioning

confidence: 99%

“…In this study, the local CMFs were derived using pre-developed jurisdiction cross-sectional SPFs, using the four pre-mentioned segmentation approaches [4]. The best-developed jurisdictions cross-sectional SPF is as follow (values between brackets [] represent the standard error) [4]: The pre-developed jurisdiction SPF was then used to derive local CMFs, as follows [52]:…”

Section: Locally Derived Cmfs Valuesmentioning

confidence: 99%

“…Road traffic crashes cost Egypt approximately 10 billion Egyptian Pounds (EGPs, about $US 1.8 billion) annually [3]. Hence, traffic safety in Egypt is considered as an area of serious importance due to the high cost of highway crashes paid by society as well as the loss of lives [4].…”

Section: Introductionmentioning

confidence: 99%

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Segmentation Effect on the Transferability of International Safety Performance Functions for Rural Roads in Egypt

Elagamy

El-Badawy

Shwaly

et al. 2020

Safety

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This paper examines the transferability of the Safety Performance Function (SPF) of the Highway Safety Manual (HSM) and other 10 international SPFs for total crashes on rural multi-lane divided roads in Egypt. Four segmentation approaches are assessed in the transferability of the international SPFs, namely: (1) one-kilometer segments (S1); (2) homogenous sections (S2); (3) variable segments with respect to the presence of curvatures (S3); and (4) variable segments with respect to the presence of both curvatures and U-turns (S4). The Mean Absolute Deviation (MAD), Mean Prediction Bias (MPB), Mean Absolute Percentage Error (MAPE), Pearson χ2 statistic, and Z-score parameters are used to evaluate the performance of the transferred models. The overdispersion parameter (k) for each transferred model and each segmentation approach is recalibrated using the local data by the maximum likelihood method. Before estimating the transferability calibration factor (Cr), three methods were used to adjust the local crash prediction of the transferred models, namely: (1) the HSM default crash modification factors (CMFs); (2) local CMFs; and (3) recalibrating the constant term of the transferred model. The latter method is found to outperform the first two methods. Besides, the results show that the segmentation method would affect the performance of the transferability process. Moreover, the Italian SPFs based on the S1 segmentation method outperforms the HSM and all of the investigated international SPFs for transferring their models to the Egyptian rural roads.

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Section: Data Descriptionmentioning

confidence: 99%

Section: Data Descriptionmentioning

confidence: 99%

Section: Data Descriptionmentioning

confidence: 99%