The people at Quantum Technologies Worldwide Inc use a composite tank with an aluminum liner to achieve a certifiable 10,000 psi tank that is hydrostatically tested to over 20,000 psi before bursting. Pretty neat, but if you put hydrogen inside it you have to keep in mind the inversion temperature of hydrogen makes such high pressures inherently self-combustable: basically even a small leak will self-ignite, and the tank will rocket or pinwheel dangerously even if it doesn't. Some people have called these tanks "hydrogen bombs", because of the destructive potential if one decides to burst. And think of the ease of access for terrorists if there is one in every motor vehicle!!! It seems futile to me considering the cost of the compressor on top of the tank, and the laws of thermodynamics do not favor compressed hydrogen as a fuel for the transportation market.