The need for survival transportation should be obvious but the kind and/or types may not be so obvious. Small and midsize cars or mini pickups are fine if you don't plan on going anywhere or are by yourself with no family. You can load all you need for most any survival situation in on of these withthe exception of group 3 type disasters. Even so you may find that it is to your advantage to add storage capacity to these vehicles to carry extra items or allow yourself more flexibility. Rooftop storage and trailer hitch reciever platforms are about the limit however without going to a dedicated trailer. Many small cars do not have the weight capacity to add much with seriously affecting the handling,durabilty and safety of the vehicle. Your owners manual will state the maximum load for your vehicle and if it is missing the tire inflation placard/decal will also give it. For most small and midsize cars this will generally be between 650 and 1000 pounds. It sounds like a lot but lets add some basic weights for a family of four. Father @ 200 lbs, mother @ 135 lbs, 10 yr old daughter @ 85 lbs and 16 yr old son @ 150 lbs for a total of 570 lbs. That leaves only 80 pounds for everything else if your car is rated for a 650 pound load. Gas weighs just over 6 pounds per gallon so you can put about 13 gallons in the tank and you are now fully loaded and you haven't even put the first thing in for equipment. Starting to get the idea that small cars and families don't mix for survival purposes? If so then read on for more information on how to do it.
Okay, for really small cars that are down at the 650 pound load capacity there really is not much you can do it you must haul a family. About the only thing you can do is add coil over springs to the shocks and gain maybe 200 pounds of capacity depending on the springs.You may have to have these springs custom made for your vehicle too which can be expensive.
As to methods of adding capacity in terms of space, Canuck in Denver has an interesting piece covering different methods in his blog here;
The reciever hitch platform I would not recommend since they require a 2 inch reciever to fit into and said reciever weighs a bunch. A roof top carrier may be okay but the best way to go is with a trailer if you must haul that family of four. If you have a family you would be far better off getting rid of the low capacity vehicle and getting a mid-size car that has a 1,000 pound load capacity or more. With this in mind I am going to treat the small car as one that will be hauling only two adults, a man and wife, or two friends whatever but a human load of 335 pounds maximum. This will leave 315 punds for fuel, cargo and anything else you may want to take. You should always round up to the nearest pound when figuring weights and for somethings the nearest 5 pounds, of which fuel is one of these. At 6.1 pounds per gallon a 13 gallon tanks holds 80 pounds of gas. So we now have a weight of 415 pounds before any cargo has been added. Subtracting 415 from 650 leaves us with 235 pounds of useable cargo capacity. This is not much especially when even the government is now recommending a 2 week supply for disaster situations as an ideal goal for preparation. At a gallon per day per person just for drinking water you are looking at approximately 225 pounds just for water for our two people. That would leave only 10 pounds for everthing else. While you may save on water weight by using a purifying filter such as a Katadyn or Berkey you still don't have a lot of weight available since the absolute minimum of water you should have is 3 days worth or 6 gallons in these example which is still approximately 48 pounds.
It should be easy to see that the only real option with a car this small is to use a trailer. A class 1 hitch should weigh about 20 pounds installed which will reduce our cargo capacity from 235 to 215 pounds IN THE VEHICLE. A vehicle this size should safely be able to tow a 1000 pound trailer equipped with surge brakes. A trailer must be properly balanced in order to trail properly. The proper balance is so that 10 percent of the total trailer weight is the weight at the hitch also known as tongue weight. So if you have a thousand pound trailer (trailer + cargo) then you have a 100 pound tongue weight (use a scale to get this right) which is subtracted from your available vehicle cargo capacity. In this example that would be 215 - 100 = 115 pounds of cargo capacity left for cargo in or on your vehicle. If you have been able to add coil over springs to your vehicle you will probably have about an extra 125 pounds of capacity for a total of 240 pounds of vehicle capacity. It may seem like a good idea to increase the trailer weight since if you double the trailer your tongue weight would still leave you with a little margin in the vehicle itself. DO NOT DO THIS, you will overload the towing capacity of the car and have serious mechancial failure and be stranded at best and dead at worst when the brakes fail to be able to stop the excess load or handling is so adversely affected that you lose control and crash.
A platform trailer of this type
equipped with these wheels
is an ideal setup for this purpose. The total weight for the trailer will be slightly under 250 (300 with surge brakes) pounds and it has a 1,000 pound load capacity which is more than you can haul. With a 1,000 pound tow limit on the vehicle minus the weight of the trailer will give you approximately 750 (700 if brakes installed) pounds of cargo capacity on the trailer. Use a canvas tarp to cover your supplies to save the weight of an enclosure. You can add 1/4 inch eye bolts to the trailer frame to provide adequate tie down points. I would recommend an extra set of wheels since flats are likely and while the tire size is common enough finding a way to get them and get them installed may not be so easy. It would be a crime to have to abandon your trailer simply because of a flat tire and the extra wheel will only cost you 40 pounds of cargo capacity. Its cheap insurance.
Mid-size car summary
All of the previously mentioned information holds true for a mid-size car as well with the following exceptions.
It will be much easier to accomodate a family in a vehicle of this size and still have some cargo capacity. without doing anything beyond having the increase in load capacity (1,000 versus 650 pounds) which used 100 percent of the small cars capacity with just the family of four and a tank of gas, there is now some actual cargo capacity. Using the family of four example you have 570 pounds in the human load, we will increase the gas tank size to 16 gallons instead of 13 so a full tank will weigh 98 pounds for a total of 668 pounds which gives you a cargo capacity of 332 pounds. Not a lot but a hell of a lot more than you had with the small car. If you add in the weight for the hitch you still have approximately 310 pounds of capacity. This is enough to be able to tow that trailer and still have some capacity left over for the vehicle. You should be able to tow the trailer with its full rated load of 1,000 pounds as well since the total weight would then be only 1,250 pounds which is within the towing ability of most mid-size cars except some of the newest models. Check your owners manual for the actual towed weight limits, some older vehicles may be rated as high as 2,000 pounds under certain conditions. 2,000 pounds is also the limit of a class 1 hitch. You may want to consider getting a 2 inch receiver type hitch and making one of the items you include in your trailer cargo a receiver mounted platform to give additional storage in case you must abandon the trailer.
It will be much easier for you to find coil over shocks or coil over spring kits for a mid-size vehicle as well and these will add significant capacity. Better yet it becomes more possible to find higher rated springs, either leaf or coil as you vehicle uses to increase the cargo capacity. Beware however that if you replace the vehicle suspension springs AND use coil over shocks that your total gain is not the total of both but will be something less. Consult a suspension expert to determine this. You will generally be better off just using one method to acheive an increase in cargo load capacity. Replacing the suspension springs will be the preferred method. If your vehicle has leaf springs you may use bolt on overload or 'helper' springs also. These will allow a normal ride when the vehicle is loaded normally but provide an assist when you fully load a vehicle.
This pretty well covers the area of small and mid-size cars as survival transportation. I will be covering full size vehicles, trucks and other vehicles in subsequent posts.