now to fig2 a portion of the drivetrain of fig1 is repeated in schematic form but with a shut off valve 11 and a pressure relief valve 12 shown between the high pressure accumulator 9 and high pressure fluid line 5 a valve controller 13 is also provided an example of an accumulator shut off valve 11 is described in commonly assigned u s pat no 6 619 325 which is incorporated herein by reference alternatively other known fluid shut off valves may be used in other structural respects the system may remain in accord with the vehicle of fig1 e g with the hydraulic motor s 7 mechanically connected to drive wheels 8 etc for safe and reliable hydrostatic operation of the vehicle of fig1 and 2 a pressure relief function provided by pressure relief valve 12 in fig2 in the high pressure system to bleed flow as necessary helps to prevent an over pressure condition in the high pressure side of the hydrostatic system capturing the excess pressure bleed flow from the pressure relief valve 12 into the high pressure accumulator 9 by bypassing the shut off valve 11 through bypass line 16 recovers energy that would otherwise be lost if.