Here is my commuting route between Alexandria and Indian Head. Old Fort is not ideal but the alternatives are 210 and Livingston road which are… not better.
https://www.strava.com/activities/610958190
Rt 225 between hwy 210 and LaPlata has nice shoulders.
There is ongoing construction on hwy210 that involves shoulder closings on both north bound and southbound sides. DO NOT RIDE ON 210 between the Beltway and Farmington Road.
Happy to discuss specifics and trouble spots if you decide you want to try it.
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