This paper presents an assessment of the roundabout  capacity model given in the new Highway Capacity  Manual 2010 (HCM 2010) with a focus in its use  in the SIDRA INTERSECTION software. The model  which is based on US research on roundabouts (NCH RP 572) can be viewed as a non-linear empirical  (regression) model with a theoretical basis in gap- acceptance methodology. The general importance of  some fundamental aspects of the model is discu ssed. Various shortcomings of the HCM 2010  roundabout capacity model listed in HCM 2010, Chapte r 21, and some related m odel extensions provided  by the SIDRA INTERSECTION software, one of the  alternative tools referred to in HCM 2010, are  discussed with a view to future development of  the HCM roundabout capacity model. Using a multilane  roundabout example given in HCM 2010, capacity and  the resulting degree of saturation (v/c ratio),  delay, level of service and queue length estimates from the  HCM 2010 model are compared with those  from the SIDRA Standard capacity model for roundabouts (using an Environment Factor of 1.2 for US  conditions). Discussions are presented in relation to th e finding of lower capacity of roundabouts in the  USA compared with Australian and UK roundabouts a nd the issue of possible increases in roundabout  capacities in the USA over time due to changes in dr iver behavior. A possible calibration of the HCM  2010 model for moderate capacity increases expected in  the future is presented making use of a driver  behavior model.

ویرایش جدید 2010 آیین نامه ظرفیت بزرگراه، فصل 21، یک مدل ظرفیت بر پایه مسیر را برای میدان های یک خط حرکت یا دو خط حرکت ارائه کرده است. این مدل، بر اساس تحقیقی در میدان های آمریکا است، همانگونه که در گزارش NCHRP 572، فصل 4 توصیف شده است (2-5)، و در راهنمای اطلاعاتی میدان TRB-FHWA پذیرفته شده است (گزارش NCHRP 672). مدل ظرفیت میدان HCM 2010 توصیف می شود و اهمیت کلی برخی ویژگی های بنیادی این مدل، مطرح می شود ....