It's always better to have a pass. The MPs have the right to refuse anyone any time. Passes are not hard to apply for. Go to the main gate near the old white house hotel. You'll need a driver's licence and the reason for needing to come on base. (Normally someone who is authorized will have to invite you) do the paperwork and wait.
Not unless they are at high alert, I have been on base plenty of time as a rider and they didn't ask me for a pass.
You will need a pass.
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