But what about zombies!! I kid. This is a completely practical exercise.

My thoughts:

1. Communications: A spare cell phone with a charger and 911-only capabilities (i.e., no SIM card). Cell phones die, get broken or stolen or left at home. Depending on the jurisdiction, a 911 operator can dispatch more than police/fire/EMS -- provided there is no immediate threat to life, they can direct a tow truck, or get a message to a family member who can respond.

2. Signalling: In the dark, red/amber colours get lost or dismissed by drivers. But nothing, absolutely nothing, cuts through the clutter like a bright white flashing LED light -- day or night. Many lights have this function (lost in the settings). Bright white LED bicycle lights (not button lights) are more foolproof. Practice with your SO how to mount on the vehicle and activate.

3. Agree: drinking water and a few snacks.

4. And more importantly: a pot to [censored] in. Women are incredibly reluctant to squat by the side of the road, especially if there's a line of vehicles. Tell her it's a "trucker's buddy" for you, and clearly mark it as such. Make sure it's smooth on top, wide-mouthed, and has a tight lid.

5. A few cheap, packaged fleece blankets. These are endlessly versatile and useful, to kneel on, sit on, wrap yourself in, etc. etc.. You can also pass them through a mostly-closed window to some panic-stricken or seemily agressive person who is just desperate because their kids are cold. It could potentially defuse an ugly situation.