We can access the AASHTO (American Association of State Highway and Transportation Officials) guide to bicycling through the San Diego City Library's (and others?) online catalog, which includes access to digital versions of various guides and resources through OverDrive or Libby. You can search for the specific title, such as "AASHTO Guide for the Development of Bicycle Facilities," on their website to find an available copy for checkout.
To find it:
Go to the San Diego City Library website.
Access their online catalog.
Search for "AASHTO Guide" or the full title "AASHTO Guide for the Development of Bicycle Facilities".
If it's available digitally through OverDrive or Libby, you can place a hold or check it out.