All-door boarding is a policy that allows passengers with valid fare cards to board buses via any available door. This program speeds up the boarding process and reduces the amount of time a transit vehicle remains stationary at a regularly scheduled stop. This waiting time, also known as dwell time, can reduce on-time performance and leads to higher operating costs for transit agencies. Metro is currently considering an expansion of their all-door boarding program, and they would like to better understand the effect of the policy on stop dwell time. I used multiple linear regression and difference in difference analysis to determine the impact of the all-door boarding policy. Multiple linear regression was used to see the effect of all-door boarding on weekdays in October 2019 when controlling for differences in boardings per stop, wheelchair boardings per stop, and articulated bus use. Difference in differences analysis was used to see how all-door boarding policy affected boarding times on Lines 720 and 754 in April 2018 vs. April 2019. My statistical models show that all-door boarding is an effective policy that significantly reduces dwell time. The multiple linear regression model shows a 6.5 seconds per stop reduction in stop waiting times due to the policy, and my difference in differences analysis shows a 16 percent reduction in dwell time per passenger boarding on Lines 720 and 754. Routes with articulated buses saw slightly higher reductions, with a 7.5 second reduction in dwell time per stop.