TY - JOUR PY - 2021// TI - Incorporating speed in a traffic conflict severity index to estimate left turn opposed crashes at signalized intersections JO - Transportation research record A1 - Anarkooli, Alireza Jafari A1 - Persaud, Bhagwant A1 - Milligan, Craig A1 - Penner, Joel A1 - Saleem, Taha SP - 214 EP - 225 VL - 2675 IS - 5 N2 - Rigorous evaluation of implemented safety treatments, especially for innovative treatments and those targeted at rare crash types, is challenging to accomplish with conventional crash-based analyses. This paper aims to address this challenge for treatments at urban signalized intersections by providing a methodology that uses surrogate measures of safety obtained from video analytics to predict changes in crashes. To develop this approach, left turn opposed traffic conflicts based on post-encroachment times, along with corresponding conflicting vehicle speeds, are first measured from video observations at signalized intersections. The conflicts are then classified into three severity levels using a risk score function defined by these measures. Multiple linear regression models are developed to relate left turn opposed crashes at the same intersections in the period 2009-2014 to the correspondingly classified conflicts. The results show strong relationships between the classified conflicts and crashes (adjusted LA - en SN - 0361-1981 UR - http://dx.doi.org/10.1177/0361198120986167 ID - ref1 ER -