Over the last fifty years, the loops and lollipops design has become the basic building block of many urban neighborhoods. In the field of traffic engineering, this combination of cul-de-sacs and loop streets is designed to discourage through traffic and improve road safety and thus has the support of many traffic engineers. Perhaps due to its intuitive appeal, few studies were conducted to examine the impact of this design on road crashes. Using the City of Calgary in Canada as a case study, this study examinesthe effects of different neighborhood street patterns on the number of reported crashes. In our study, crashes are converted into Equivalent Property Damage Only (EPDO) crashes using various weighting factors to check thesensitivity of our finding. Our results suggest that currently popular road patterns such as warped parallel, loops and lollipops are safer than traditional grid-iron pattern. Moreover, this result is quite robust with respect to different severity weights or aggregation schemes, albeit with some variations in the absolute values of the estimated effects. However, changing the aggregation scheme did have a significant effect on some of thecontrol variables used in the model, especially the socioeconomic characteristics, even though most of the road features and land use estimates remained robust.
Abstract