How long after taking Sumatriptan(Imitrex) is it considered safe to drive?

[Karupin]

I would like to know how long  after taking Sumatriptan/Imitrex could any drowsiness side effect be considered to have worn off for when I get a migraine away from home and have no reasonable option to get home without driving myself.  A few years ago, I got a migraine while some distance from home.  I do not drive with a migraine.  I took a sumitriptan, then settled back in my car (in a parking lot) with my eyes closed since the medication works better for me if I can "cat nap", preferably in the dark, for 15-30 min. (light variations/strobic effects are a primary migraine trigger for me).  Although it is a listed side effect, sumatriptan doesn't actually make me drowsy.  A police officer disturbed me for a "wellness check" (apparently someone was worried about me).  When I said I was fine, just waiting for my headache to clear up completely before driving home (he did not ask what medication I took), the officer asked for my driver's license and told me he would not allow me to drive home as I would be "driving under the influence".  Fortunately, my brother was actually not travelling for business that day but he had to make a 90 mile round trip to get me and repeat the trip a few days later in order to retrieve my vehicle.  Many places here in Alaska have very limited options regarding public transportation  - nor is a 40 mile cab ride cheap!  (Note - you can actually get a DUI for napping in your vehicle in a parking lot after taking medication, as well as doing the same after drinking.)