Build your car kit for the ninety-minute wait, not the photo

Quick answer: Buy a lithium jump starter, a 12-volt tire inflator, a real flashlight, a warm layer, water, and a power bank. Then go find your spare tire and your locking lug nut key before you ever need them.

Picture it. It's 7:40 on a January evening, you're on the shoulder of a two-lane highway, the battery's dead, and your phone is at 11 percent. Roadside assistance says the truck will be there in an hour and forty minutes. Nothing in the kit you bought at the auto parts store helps with any of that. The jumper cables need a second car. The bandages are for a paper cut. The "emergency poncho" is a garbage bag with ambitions.

Most cars don't strand people dramatically. They strand them boringly. A battery dies, a tire goes flat, or you sit and wait in the cold or the heat. Build the kit around those, in that order, and you'll be the one who drives away.

Start with the car you actually own

Before you buy anything, open the trunk and lift the floor.

A lot of newer cars don't carry a spare at all. They ship with a can of sealant and a little compressor instead. You need to know which car you have now, in your driveway, not on the shoulder with a semi blowing past.

If you do have a spare, check three things:

• Pressure. Compact spares often run at 60 psi, much higher than your regular tires. The number's printed on the spare itself or on the placard in the driver's door jamb. A spare that's been sitting flat for four years is a very heavy paperweight.
• The jack and lug wrench. Make sure they're there and that you know how they fit together. Previous owners lose these.
• The locking lug nut key. If your wheels have one odd-shaped lug nut each, you need a special socket to remove it. It's usually in the glovebox, the center console or a pocket by the spare. If it's missing, nobody's changing that tire on the roadside, including the tow driver. Find it and put it with the jack.

Then change a tire once, in daylight, on flat pavement, with nobody watching the clock. It takes most people twenty to thirty minutes the first time and half that the second. The owner's manual shows the jack points. Loosen the lug nuts before you lift the car, because a wheel in the air just spins. That one detail is the whole difference between a frustrating afternoon and a finished job.

You don't have to love doing it. You just have to know you can.

The kit, by the job it does

For a dead battery

• A lithium jump starter pack. It's about the size of a hardcover book and it starts your car without a second vehicle. The NOCO Boost line is a common, well-regarded choice. Match the rating to your engine (a big V8 truck needs more than a compact four-cylinder) and read the manual for which clamp goes where.
• Jumper cables too, if you have room. They're cheap, they never run flat, and they let you help somebody else.

For a flat tire

• A 12-volt tire inflator that plugs into the car's power outlet. A slow leak plus an inflator often gets you to a tire shop on your own tire.
• A can of tire sealant such as Fix-a-Flat or Slime as a backup. It's a temporary fix for small punctures in the tread, not sidewall damage. Tell the shop you used it.
• A pair of work gloves. Lug nuts are filthy and occasionally sharp.
• A short piece of 2x6 board, about a foot long. It gives the jack a solid base on soft dirt or gravel. This is the item nobody includes and everybody wishes they had.

For being seen

• Three reflective warning triangles or LED road flares. Set them well behind the car so traffic has time to react.
• A reflective vest. It costs less than lunch.
• A real flashlight or headlamp with fresh batteries. A headlamp is better, because you'll need both hands.

For the wait

• A power bank, fully charged, plus a charging cable that actually fits your phone.
• A wool blanket or a heavy fleece, and a knit hat. Cars lose heat fast once the engine's off.
• Water and a few granola bars or nuts that won't melt or freeze into a brick.
• An index card with your roadside assistance number, your insurance policy number and two phone numbers you know will answer. Write it by hand. A dead phone takes your contacts with it.

Small, but you'll be glad

• A basic first aid kit with real-sized bandages, gauze and tape.
• A multi-tool, a roll of duct tape and some zip ties.
• A small towel and a few wet wipes.

Put it all in one bin or duffel that's strapped down or wedged in. A loose jump starter becomes a projectile in a hard stop.

What we'd buy, and what we'd skip

Buy: the jump starter first. It solves the most common breakdown, and it solves it without asking a stranger for help. Then the inflator, then the headlamp.

Skip: the giant all-in-one kit with a hundred pieces, half of them tiny bandages and a toy flashlight. Skip the decorative "her car kit" in a cute bag. A flat tire doesn't care what the bag looks like, and neither should you.

The honest trade-off: lithium jump starters lose charge sitting in the car, and extreme heat and cold are hard on them. Bring yours inside and top it off every few months, or when you change the clocks. If you'll never remember, a good set of jumper cables is the more reliable choice, even though it needs a second car.

Winter and summer change the list

In winter, add an ice scraper with a brush, a compact shovel, a bag of kitty litter or sand for traction under a spinning tire, and chemical hand warmers. Keep your gas tank above half. It's extra weight that also happens to be heat. If you're stuck in snow and running the engine for warmth, clear snow away from the tailpipe first so exhaust doesn't back up into the car.

In summer, double the water and swap the wool blanket for a sunshade and a wide-brimmed hat. Rotate the water bottles every few months so you're not drinking something that's spent a July baking in the trunk.

On the shoulder

Get as far off the road as you can, hazards on. On a busy highway where you can't get fully clear, the safest place is often inside the car, buckled in, while you call for help. If you have to get out, use the door away from traffic.

If somebody stops to offer help and something feels off, you don't owe them a conversation. Thank them through a cracked window, tell them help's on the way, and let them drive on. Polite and firm is a complete answer.

If you lawfully carry, know your state's rules for carrying in a vehicle, and the rules in every state on your route. They differ, sometimes a lot, so check before the trip and ask a local attorney or your state's official resources if anything's unclear.

When it's somebody else's breakdown

A full kit makes you useful to other people, and that's half the point of having one. A coworker with a dead battery in the parking lot. A neighbor whose tire's going soft. You can fix that in ten minutes.

You still get to use judgment. Alone, at night, on an empty road, the right way to help a stranded driver is often to call it in and keep going. That isn't cold. It's sensible, and it still gets them help.

And keep the old code. If you use anything from your kit, or somebody else's, replace it that same week. Lend your jump starter and it should come back charged. Borrow one and send it back charged and wiped down. Use the last bottle of water and buy a case.

Twice a year, ten minutes

Pick two dates you'll remember, like the clock changes in spring and fall. Charge the jump starter and the power bank. Check the spare's pressure. Swap the water and snacks. Test the flashlight. Make sure the lug nut key is still where you put it.

Ten minutes in your driveway on a Saturday morning, so a breakdown at 7:40 on a January night takes fifteen.