This research: (1) examines the impact of missing data from permanent counters on the accuracy of the AADT; and (2) analyses the effect of varying short term count durations on the accuracy of AADT estimates. Data gaps can occur at permanent counters due to equipment malfunction and lane closures and can result in no available useable data. For short term counts a balance between accuracy and cost efficiency drives a need for an ideal count duration. Using data from Manitoba’s permanent counters, controlled data gaps and simulated short term counts were created to estimate AADTs. 150,000 AADTs were obtained from the analysis and were then compared to the true AADT to determine the overall error. The findings of this research showed that larger data gaps and shorter duration counts carry more error. Additionally, factors including month of the year and traffic pattern group impact AADT estimates illustrating the need for context sensitivity when rejecting data from a permanent counter and selecting an appropriate count duration. / October 2015