| dc.description.abstract | The goal of this thesis was to examine the effect of incidents and adverse weather (rain) on capacity and Free-Flow Speed (FFS). Data were collected from multiple freeway segments in Kansas City, Kansas from 2014 to 2018. In this thesis, capacities and free-flow speed were measured during four conditions: (1) base conditions, (2) adverse weather only, (3) incidents only, and (4) adverse weather and incidents. Freeway flow breakdown was assumed to occur when speed dropped below 75% of the Free-Flow Speed. This definition was used for measuring capacity during non-incident conditions. Average discharge flow, i.e., the flow after the breakdown and during congested conditions with duration of at least 15 minutes, was used to identify capacity under incidents conditions. Capacity Adjustment Factors (CAF), and Speed Adjustment Factors (SAF) were established in this thesis to identify the remaining capacity or the Free-Flow Speed reduction during an incident or adverse weather conditions. CAFs were found by comparing the average capacity during base conditions to the average capacity during adverse weather (rain), incidents, or adverse weather and incidents. Likewise, SAFs were estimated by comparing average FFS during base conditions and average FFS during rain, incident, or rain and incidents. CAFs and SAFs were primarily developed for use within the 6th edition of Highway Capacity Manual (HCM6); although the manual does not provide SAFs for incidents. Also, the effect of incidents along with rain on capacity and FFS is assumed to be additive in the HCM6, but this assumption has not been validated with actual data. The results from this thesis indicated that rain has minimal effect on capacity. Also, only FFS on three-lanes freeways was impacted by rain. It was also found that incidents and incidents during rain had an impact on capacity and FFS. The measurement location with respect to the closure during incidents was considered in this research. However, according to the statistical analysis, the location was found to be significant only for incidents during rainy conditions, and only at freeways with two and three lanes. | |
