the following detailed description illustrates the invention by way of example and not by way of limitation . the description enables one skilled in the art to make and use the present disclosure , and describes several embodiments , adaptations , variations , alternatives , and uses of the present disclosure , including what is presently believed to be the best mode of carrying out the present disclosure . the present disclosure provides a method and apparatus for automating a rolling movement of a vehicle during a rolling compensation procedure of a vehicle wheel alignment service . at the start of the vehicle wheel alignment service , the vehicle is driven onto , or position on , a supporting structure 100 , such as a pair of vehicle support runways 102 associated with a vehicle lift or measurement station . one such vehicle support runway 102 is shown in fig1 a and 1b . within the support structure 100 , an actuation mechanism 200 under control of a vehicle wheel alignment service system ( not shown ) is provided to enable inclination of the lift ramp segment 104 of the support runway 102 by the elevation of one end of a lift ramp segment 104 beneath one or more of the vehicle wheels ( best seen in fig1 b ), causing the vehicle to roll down the inclined lift ramp segment 104 a short distance along the support runway 102 in response to the force of gravity , without the need for the operator to manually push or pull the vehicle . the actuation mechanism 200 may be pneumatically operated , hydraulically operated , or mechanically driven , to elevate one end of the lift ramp segment 104 to a sufficient height to achieve the desired rolling movement of the vehicle . preferably , the vehicle wheel alignment service system may be configured to selectively control the tilting elevation of the lift ramp segment 104 to achieve a desired rate of rolling movement , and / or a desired distance of rolling movement for the vehicle . as seen in fig4 a , 4b , and 5 , an exemplary actuation mechanism 200 is disposed beneath the vehicle support surface 105 of the lift ramp segment 104 , adjacent the end to be elevated . the actuation mechanism may be contained within a protective housing 202 , and preferably includes a power unit 204 adapted to receive external commands , together with one or more cylinder assemblies 206 a , 206 b each containing an actuating piston 208 . each actuating piston 208 is driven by the associated cylinder assemblies to between a retracted position wherein the lift ramp segment 104 is disposed substantially level with respect to the vehicle support runway 102 ( such as seen in fig3 ), and an extended position wherein the extension of the actuating piston 208 inclines the lift ramp segment 104 with respect to the vehicle support runway 102 ( such as seen in fig4 a and 4b ). those of ordinary skill in the art will readily recognize that the specific configuration of the actuation mechanism 200 may be varied in accordance with the specific configuration of the vehicle supporting structure 100 , and that any suitable actuation mechanism which can be controlled by external commands from a vehicle wheel alignment system or an operator to selectively incline the lift ramp segment 104 may be utilized within the scope of the present disclosure . before , during , and after the rolling movement of the vehicle down an inclined lift ramp segment 104 , conventional measurements may be obtained by an associated vehicle wheel alignment service system ( not shown ) as required to complete a rolling compensation procedure using sensors ( not shown ) or optical targets as seen in fig1 a and 1b , mounted to the individual wheels of the rolling vehicle . once the vehicle has rolled to the desired position on the supporting structure 102 , the inclined lift ramp segment 104 is lowered and returned to the initial horizontal position by the actuating mechanism 200 , such that it is generally coplanar with the other vehicle support surfaces of the supporting structure 102 . in one embodiment , the rolling movement and position of the vehicle wheel is monitored by the vehicle wheel alignment service system using the sensors or optical targets , and the actuating mechanism 200 is controlled by the vehicle wheel alignment service system using a feedback control circuit to achieve a desired rate of rolling movement and / or positioning of the vehicle wheel through controlled inclination of the lift ramp segment 104 . in addition to enabling rolling movement of the vehicle such as during a rolling compensation procedure , the actuation mechanisms 200 for the lift ramp segments 104 may be controlled by the operator or vehicle wheel alignment system to carry out vehicle service procedures or measurements other than rolling compensation . for example , with the weight of a vehicle supported above the runway surfaces 105 of the support structure 102 by a separate jacking mechanism ( not shown ), a vehicle service system may be configured to direct the actuating mechanism 200 to partially incline or elevate the lift ramp segments 104 to impart a vertical load to a supported vehicle wheel , without causing the wheel to roll , thereby enabling the vehicle service system to observe the responses of the vehicle wheel suspension components in both loaded and unloaded conditions . by monitoring the responses of the vehicle wheel suspension components to the imparted vertical loads , excessive play or looseness may be identified by the vehicle service system , and suitable messages for correction provided to an operator . those of ordinary skill in the art will recognize that the present disclosure is not limited to a specific use of the disclosed lift ramp segments 104 , and that there may be other operations and / or vehicle service procedures wherein it may be useful to impart a vertical load to one or more wheels of a supported vehicle . for example , it may be beneficial to impart a vertical load to a single wheel of a vehicle using the a single lift ramp segment 104 in order to compress a vehicle suspension member during removal or repair . in one embodiment of the vehicle support structure 100 disclosed herein , after the vehicle is rolled forward by the tilting elevation of the lift ramp segment 104 , the steered wheels of the vehicle will preferably come to rest on associated turnplates 110 within the support runway 102 or which are incorporated into the upper surface of the lift ramp segments 104 themselves . the turnplates 110 are adapted to enable automation of the steering movement of the steered vehicle wheels during vehicle wheel alignment service procedures , such as caster steer , which require a range of steered wheel movement . as shown in u . s . pat . no . 7 , 308 , 971 b2 to liebetreu et al ., which is herein incorporated by reference , turnplates 110 are mechanically configured to support the vehicle steered wheels , and to enable both rotational and independent translational movement of the wheels during steering motion . by disassociating the rotational movement of the turnplate from the translational movement , the turnplate can accommodate offset positioning of the vehicle wheel from the turnplate rotational axis , as well as translational movement due to the ackerman effect from the vehicle wheel suspension geometry . to automate the steering movement , a turnplate actuation mechanism preferably under control of the vehicle wheel alignment service system , but optionally controlled by the operator , is provided within at least one of the turnplates 110 , but preferably within both front turnplates ( i . e . one for each steered wheel of the vehicle ). the turnplate actuation mechanism may be pneumatically driven , hydraulically driven , or mechanically driven , and is configured to rotate each turnplate 110 in response to commands from the operator or vehicle wheel alignment service system , effectively steering the vehicle steered wheels through a range of desired steering movement . the turnplate actuation mechanism is configured to facilitate the acquisition of required steered wheel measurements across the desired range of steering motion without the need for the operator to manually move the steered vehicle wheels or to enter the vehicle and turn the steering wheel . in order to accommodate any misalignment between the rotational axis of the turnplates 110 and the steering axis of the steered vehicle wheel , the turnplate actuation mechanism for the rotational movement , and the upper surfaces of the turnplate 110 are configured for rotational movement independent from the translational movement of the turnplate 110 , such that each vehicle steered wheel is permitted to freely move about a steering arc in response to the driven rotational movement from the turnplate 110 . during a vehicle wheel alignment service procedure which requires a steering movement of the vehicle wheels , such as a caster steer measurement procedure , the operator or the vehicle wheel alignment measurement system controls the operation of the turnplate actuation mechanism in the turnplates 110 to move the steered vehicle wheels supported on the turnplates 110 through the required range of steering motion , while acquiring the necessary measurements from the sensors associated with the wheels in a traditional manner . the measurements may be conventionally acquired during the steering movement , or the steering movement may be stopped by the vehicle wheel alignment service system at various rotational positions for stationary measurements to be obtained . the specific range of steering movement through which the steered wheels are driven by the turnplates 110 may be controlled by mechanical stops incorporated into the turnplate actuation mechanism , or may be regulated by the observation of targets and / or sensors associated with the steered vehicle wheels by the vehicle wheel alignment service system . in addition to facilitating caster steering measurement procedures , those of ordinary skill will recognize that the actuated turnplates 110 of the present disclosure may be utilized by a vehicle wheel alignment service system to carry out a variety of vehicle wheel alignment and / or service procedures which require controlled steering movement of the vehicle steered wheels . for example , by controlling the turnplate actuation mechanisms in each turnplate assembly 110 independently , a vehicle wheel alignment service system may engage the turnplate assemblies 110 to automatically apply opposite rotational forces simultaneously to each steered wheel of a vehicle . by observing the resulting reactions in the vehicle steered wheels , looseness or play in the various vehicle suspension and steering system components may be identified , and suitable warning messages displayed to an operator indicating the need for vehicle repair or service . correspondingly , for some vehicle service procedures , the steered vehicle wheels are required to remain stationary , and should not be free for steering movement . in addition to driving the turnplate assemblies 110 through a range of steering movement , the turnplate actuation mechanisms under control of the vehicle wheel alignment service system may be utilized to hold or lock the turnplates 110 in a desired position , preventing unrestrained steering movement of the vehicle steered wheels during a vehicle service procedure or measurement process . those of ordinary skill in the art will recognize that not all vehicle support structures 100 will necessarily incorporate turnplate assemblies , such as the actuated turnplate assemblies 110 . for example , a vehicle inspection center and / or quick - lube oil change center may not be configured to carry out full - service vehicle wheel alignment procedures which require full - range steering motion of the vehicle steerable wheels as provided by turnplate assemblies . however , the vehicle wheel alignment inspection procedures conducted by such facilities may require the steerable wheels to have at least a limited range of free motion during the vehicle wheel alignment service and / or inspection procedures . accordingly , in one embodiment , the lift ramp segments 104 upon which the vehicle wheels are disposed may incorporate suitable support structures , as shown at fig6 and 7 , to function additionally as locking slip - plates and to provide a limited range of free movement both laterally and transversely for a supported vehicle wheel . to selectively permit free movement both laterally and transversely of the supported vehicle wheels , the vehicle support surface 105 of the lift ramp segments 104 is secured on an underside surface to accommodating mountings 300 and a locking mechanism 400 , as best seen in fig6 . preferably , the set of accommodating mountings 300 couple the vehicle support surface 105 to the internal structure of the lift ramp segment 104 . each accommodating mounting , as best see in fig7 , consists of a flexible protective bellows 302 which seals and encloses the components of the accommodating mounting 300 . within the protective bellows , an upper mount 304 couples the vehicle support surface 105 to an upper support plate 306 . the upper support plate 306 , in turn , rests on a ball bearing assembly 314 supported by a lower plate 316 coupled to the fixed structure of the lift ramp segment 104 . the ball bearing assembly 314 contains a plurality of ball bearings 312 in a planar arrangement within a retaining cage 311 . the ball bearing assembly 314 is permitted a limited range of motion within a horizontal plane between the upper and lower support plates 306 , 316 , and is restrained within a triad of extension springs 308 secured by dowel pins 310 to the lift ramp segment support structure . a centering force imparted on the ball bearing assembly 314 by the triad of extension springs 308 increases the further the ball bearing assembly moves off - center relative to the upper and lower support plates 306 , 316 , effectively biasing the ball bearing assembly towards a centered location . as can be appreciated by those skilled in the art , the vehicle support surface 105 , coupled to the accommodating mountings 300 in an unlocked configuration , has a limited freedom of movement within the plane of the mountings 300 due to the ball bearing assemblies 314 . in order to prevent movement of the vehicle support surface 105 , the locking mechanism 400 may be actuated , pivoting one or more engaging members 402 into contact with restraining surfaces 404 rigidly coupled to the vehicle support surface 105 . the frictional engagement and contact forces between the engaging members 402 , which are secured to the lift ramp segment support structure , and the restraining surfaces 404 secures the vehicle support surface 105 in a centered and locked position for so long as the locking mechanism 400 remains actuated . the locking mechanism 400 may be pneumatically operated , hydraulically operated , or mechanically operated in response to commands from an associated vehicle wheel alignment system , vehicle service console , or operator . those of ordinary skill in the art will readily recognize that the specific configuration and mechanism of either the accommodating mountings 300 or the locking mechanism 400 adapted to enable and control a limited range of movement for the vehicle support surface 105 of the lift ramp segments 104 may be varied from the specific configurations described herein and shown in the figures without departing from the scope of the present disclosure . for example , structures designed to accommodate vehicles of greater than average weight may require correspondingly greater numbers of accommodating mountings and / or different types of locking mechanisms , such as those set forth in u . s . pat . no . 7 , 308 , 971 b2 to liebetreu et al . by integrating the various vehicle support structure embodiments of the present disclosure with a computerized vehicle wheel alignment system , it will be recognized that a high degree of automation may be achieved in the measurement and evaluation of a vehicle &# 39 ; s wheel alignment settings . for example , a computerized vehicle wheel alignment system which is in communication with a vehicle support structure 100 incorporating actuated lift ramp segments 104 and / or actuated turnplate assemblies 110 can automate many wheel alignment data acquisition procedures which require rolling movement of the vehicle and / or steering movement of the vehicle &# 39 ; s steered wheels . in an exemplary vehicle wheel alignment service process , illustrated in fig1 a - 10d , a vehicle is driven onto a vehicle support structure 100 of the present disclosure , and positioned with two wheels on the actuated lift ramp segments 104 , as seen in fig1 a . the operator proceeds to install any required wheel alignment sensors or optical targets to the vehicle wheels , and optionally raise the vehicle support structure 100 to a service height . the action of raising the vehicle support structure 100 to the service height may be communicated to the vehicle wheel alignment system , and optionally initiate the start of the vehicle wheel alignment procedures by the vehicle wheel alignment service system , or the operator may provide the system with an indication to start , such as by providing a vin number or other start indication . alternatively , for a machine vision vehicle wheel alignment system , observation of the presence of one or more optical targets mounted to the vehicle wheels and positioned within a selected region in a camera field of view , such as by the lifting of the vehicle on a vehicle lift rack to a “ service ” or “ working ” height , may be used to initiate the start of the vehicle wheel alignment procedures . at this point , the vehicle wheel alignment service system may begin the service procedures by automatically conducting the required rolling compensation procedures to obtain the necessary sensor and / or target calibrations . the rolling compensation procedure is carried out automatically as the vehicle wheel alignment service system commands the actuated lift ramp segments 104 to incline above the horizontal surfaces of the vehicle support structure 100 , imparting a controlled rolling movement to the vehicle in response to the force of gravity , as seen in fig1 b . preferably , the inclination angle and duration of the inclination of the actuated lift ramp segment is controlled by the vehicle wheel alignment service system to impart a desired rate of rolling movement to the vehicle , and to ensure that the vehicle rolls a preferred distance along the lift ramp segment 104 , coming to rest at a desired location , such as on an integrated turnplate assembly 110 . as seen in fig1 c , the inclination of the lift ramp segment 104 rolls the vehicle such that the front steered wheels of the vehicle come to rest on the associated turnplate assemblies 110 ( if present ), at which point the lift ramp segment 104 is returned to the horizontal rest position ( fig1 d ), enabling the vehicle wheel alignment service system to continue with subsequent procedures , such as an automated caster steer measurement procedure . for systems including actuated turnplate assemblies 110 , the vehicle wheel alignment system is configured to direct the actuating mechanism in the turnplate assemblies 110 to rotate the steered vehicle wheels through a range of steering movement sufficient to obtain the required caster steer measurements from the associated sensors and / or optical targets on the steered vehicle wheels during an automated caster steer measurement procedure . upon completion of the automated caster steer measurement procedures , the steered vehicle wheels are returned to the straight - ahead steered position by the wheel alignment system controlled - actuation of the turnplate assembly 110 , and additional vehicle wheel alignment angle measurements such as toe , camber , and caster , are obtained as is conventional during a wheel alignment measurement procedure . it will be readily recognized that by configuring a vehicle wheel alignment system to automate one or more of the measurement and compensation procedures required during a vehicle wheel alignment service procedure , through the use of actuated components on a vehicle support structure 100 such as lift ramp segments 104 or turnplates 110 , improvements in measurement accuracy and efficiency may be obtained . it will further be recognized that the specific mechanical constructions of the lift ramp segment 104 may be varied or modified without departing from the scope of the present disclosure . indeed , as seen in fig8 and fig9 , a fundamental concept of the present disclosure , i . e ., the imparting of gravity - assisted rolling movement to a vehicle as part of vehicle wheel alignment measurement or correction procedure need not be done by mechanical elevation of a lift ramp segment at all . rather , in an embodiment particularly suitable for heavy vehicles and / or trucks , the vehicle is initially position on a solid support surface , at the top of a descending roll ramp segment . the sensors or optical targets are secured to the vehicle wheels in the customary manner . when it is necessary to roll the vehicle forward for compensation and / or measurement procedures , the associated vehicle service system provides a suitable indication to the service technician or operator , who gently pushes the vehicle forward onto the descending roll ramp segment . alternatively , an actuating mechanism could initiate the roll . once the vehicle wheels cross onto the descending roll ramp segments , the force of gravity will maintain the rolling movement of the vehicle as it descends down the ramp segment , and comes to rest at a final position adjacent a wheel stop or bumper configured to prevent further forward motion . the use of descending roll ramp on a vehicle support structure provides a means by which an operator or service technician can at least partially automate and safely roll a vehicle as required for compensation or service procedures , without being required to exert large pushing forces . ideally , the length and slope of the descending roll ramp as shown in fig8 and 9 is selected to impart only the necessary rate of rolling motion and rolling distance to the vehicles with which it is being utilized . to accommodate different weights and / or sized of vehicles , a set of descending roll ramps having different lengths and / or inclinations may be constructed as interchangeable components of the vehicle support structure . the present disclosure can be embodied in - part in the form of computer - implemented processes and apparatuses for practicing those processes . the present disclosure can also be embodied in - part in the form of computer program code containing instructions embodied in tangible media , such as floppy diskettes , cd - roms , hard drives , or another computer readable storage medium , wherein , when the computer program code is loaded into , and executed by , an electronic device such as a computer , micro - processor or logic circuit , the device becomes an apparatus for practicing the present disclosure . the present disclosure can also be embodied in - part in the form of computer program code , for example , whether stored in a storage medium , loaded into and / or executed by a computer , or transmitted over some transmission medium , such as over electrical wiring or cabling , through fiber optics , or via electromagnetic radiation , wherein , when the computer program code is loaded into and executed by a computer , the computer becomes an apparatus for practicing the present disclosure . when implemented in a general - purpose microprocessor , the computer program code segments configure the microprocessor to create specific logic circuits . as various changes could be made in the above constructions without departing from the scope of the disclosure , it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense .