You can find suggestions for everything from an economy car up to a Monster Truck by searching “bug out vehicle”. There are many vehicles which can be used in various situations. Recently, I bought five mountain bicycles for my family. They are mainly used for exercise and recreation.
Since I’ve ridden mine on paved and dirt roads, my perspective has changed. It would be great to use a bike as a way of transport when you are trying to save fuel in a vehicle or when the fuel runs out. You can buy a brand-new mountain bike at Wally-World for as low as $80. Spend a bit more (or a lot) to get a high-quality bike. Spending more money will make your bike lighter and perform better.
Craigslist has a lot of used bikes for sale at a discount. The two bikes I bought cost $100 each. The bikes were brand new, but had good parts (gears, shifters, etc.). They have been doing great so far.
The parts should last and spare tubes, tires and brakes can be purchased for a low price. A small bag under my seat can be used to store a few items. With a small pack, I’ve ridden without any problems. Although I haven’t done it, I think a heavier pack will make riding more challenging from the standpoint of top-heavy – especially on trails. There are saddlebags that would be great for carrying supplies.
There’s always an alternative. It’s good to have choices.