It's about 37-38" wide (slightly rounded at the back), about 33" long with the back seats up and around 17" high at the far back (rapidly increasing as you go forward). The safest way to tell whether the wheelchair fits is to try it out at a Volt dealer.
See if your dealer will let you take an extended test drive. It will not only let you figure out if the trunk is big enough, it will let you a better feel for getting in and out of the car on a regular basis. No point if the wheelchair fits if your daughter can't get in and out without too much difficulty.
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