in what follows , there will be described start control by an automatic transmission control unit with reference to fig1 to 5 . fig1 illustrates a control system . a throttle sensor 14 is provided on a throttle valve 22 of an engine 11 for detecting throttle opening . the throttle opening of the throttle valve 22 changes correspondingly to the amount of stepping by an operator on an acceleration pedal 21 to increase and decrease output revolution speed of the engine 11 . a revolution sensor 15 provided on the engine 11 detects the speed of revolution of an output shaft of the engine 11 . speed change modes of 6 classes of an automatic transmission 12 : forward 3 , reverse 1 , neutral , and parking are set with a shift lever 23 . these speed change modes are detected by a rotary switch 16 mounted on the automatic transmission 12 . the revolution speed of the output shaft of the automatic transmission 12 detected by a vehicle speed sensor 18 corresponds to a vehicle speed level of an automobile . the total five speed change gears of forward 4 and reverse 1 can be set to the automatic transmission 12 . setting of the speed change gears is executed by on and off combinations of a plurality of solenoid valves 17 provided on the automatic transmission 12 . the automatic transmission control unit 13 for controlling the automatic transmission 12 incorporates outputs of the throttle sensor 14 , revolution sensor 15 , rotary switch 16 , vehicle speed sensor 18 , other sensors and instruments and executes necessary arithmetic operation processings , and estimates a speed change gear to be set to the automatic transmission under operation conditions at that time to switch the on - off combinations of the solenoid valves 17 . the automatic transmission control unit 13 allocates the first gear and the second gear as illustrated in fig2 in the ordinary control , and switches the speed change gears of the automatic transmission 12 in response to a combination of a vehicle speed v estimated from an output of the vehicle speed sensor 18 and a throttle opening th estimated from an output of the throttle opening sensor 14 . for the shift - up gear change there are allocated the first gear in a region located on the left side of a speed change line l1 , the second gear between the speed change line l1 and the speed change line l3 , and the third gear in a region located on the right side of the speed change line l3 . in contrast , for the shift - down gear change there are allocated the first gear in a region located on the left side of the speed change line l2 , the second gear between the speed change line l2 and the speed change line l4 , and the third gear in a region on the right side of the speed change line l4 . there is further allocated a speed change line of the fourth gear ( not illustrated ) on the right side of the speed change lines l3 , l4 . for example , in the acceleration state indicated by an arrow p1 , there are executed the shift - up gear change from the first gear to the second gear at a point e where the arrow intersects the speed change line l1 , and the shift - up gear change from the second gear to the third gear at a point f where the arrow intersects the speed change line l3 . further , in the deceleration state indicated by an arrow p2 , there are executed the shift - down gear change from the third gear to the second gear at a point g where the arrow p2 intersects the speed change line l4 , and the shift - down gear change from the second gear to the first gear at a point h where the arrow intersects the speed change line l2 . however , when an automobile has been stopped , the ordinary control is replaced for the creep suppression control , and the second gear is set to the automatic transmission 12 to increase the speed change ratio whereby there is prevented the creep where the automobile advances at a fine speed owing to the idle rotation of the engine 11 . return to the ordinary control from the creep suppression control is immediately executed when the acceleration pedal 21 is strongly stepped on , while it is executed at the stage the automobile has been completely started and reaches a predetermined speed when the acceleration pedal 21 is mildly stepped on . herein , the strength of the stepping on the acceleration pedal 21 is determined by calculating the changing rate vth of the throttle opening th and judging whether the rate vth is less than a predetermined rate ( a ). more specifically , when the changing rate vth of the throttle opening th exceeds the predetermined value ( a ), a region b in fig4 is used as a range to which the creep suppression control is applicable . in contrast , when the rate vth is the set value ( a ) or lower , an extended region a illustrated in fig3 is used as the range to which the creep suppression control is applicable . for example , in an acceleration pattern lying from the point a to d illustrated in fig3 and 4 , the throttle opening th does not reach the threshold th1 , so that setting of the second gear by the creep suppression control is continued until the operation reaches the vehicle speed v2 . since the vehicle speed v2 is defined between the speed change line l1 and the speed change line l3 , the first gear is not quite used in such a start acceleration state . in an acceleration pattern lying from the point a to c illustrated in fig3 since the rate vth is the set value ( a ) or less even if the throttle opening th exceeds a threshold th1 , setting of the second gear by the creep suppression control is continued until the vehicle speed v1 or a threshold th2 is reached . in such a start acceleration state , the operation returns to the ordinary control for the first time after the throttle opening th reaches the threshold th2 and is shifted to the first gear , and hence powerful acceleration with the first gear is initiated . in an acceleration pattern lying from the point a to b illustrated in fig4 an operator strongly steps on the acceleration pedal and the rate vth exceeds the set value ( a ) at the time the throttle opening th exceeds the threshold th1 , so that the operation immediately returns to the ordinary control and is shifted down to the first gear , and hence powerful acceleration with the first gear is initiated . fig5 is a flow chart illustrating such creep suppression control . the control flow is inserted in an ordinary control flow in the automatic transmission control unit 13 . in step 111 , continuation / prohibition of the creep suppression control is judged . continuation is determined when the rotary switch 16 is set to the forward advance mode and the vehicle speed v is 0 or when a continuation flag set in later step 126 is 1 . otherwise , the operationn goes to step 119 for execution of the ordinary control . with the continuation there is executed the creep suppression control constructed with steps 112 to 118 and steps 120 to 126 . in step 112 , it is determined whether the speed change gear of the automatic transmission 12 is the second gear or not . since with the vehicle speed v being 0 and in the early stage of the vehicle being stopped , the speed change gear of the automatic transmission 12 is the first gear , the operation goes from step 120 to 122 and is shifted up to the second gear , and the continuation flag is set to 1 in step 126 . thereafter , the operation is determined to be at the second gear in step 112 to successively suppress the creep during the stoppage of the vehicle . in step 113 , the changing rate vth of the throttle opening th is estimated using stored data of the momentary throttle opening th . in step 114 , it is determined whether the estimated changing rate vth of the throttle opening exceeds the set value ( a ) or not . when the rate vth is the set value ( a ) or less , the operation goes to step 124 where it is judged whether the combination of the vehicle speed v and the throttle opening th falls within the region a or not . if the operation is determined to be within the region a , the operation goes to step 126 to keep the second gear with the creep suppression control . when the rate vth exceeds the set value ( a ), the operation goes to step 115 where it is determined whether the throttle opening th exceeds the threshold th1 or not . when the throttle opening th is the threshold th1 or less , the operation goes to step 125 where it is determined whether the combination of the vehicle speed v and the throttle opening th falls within the region b or not . if the combination is determined to fall within the region b , the operation goes to step 126 where the second gear by the creep suppression control is maintained . in the cases where the throttle opening th is determined to be the threshold th1 or more in step 115 , or the combination is determined to be outside the region a in step 124 or outside the region b in step 125 , the operation is returned to the ordinary speed change control . if the combination of the throttle opening th and the vehicle speed v already falls within the second gear region , the operation goes from step 116 to step 118 where the continuation flag is set to 0 . if the combination stays within the first gear region , the operation goes from step 116 to 117 where it is shifted down to the first gear , and thereafter the operation goes to step 118 where the continuation flag is set to 0 . by the fact that the continuation flag is set to 0 in step 118 the creep suppression control is prohibited until the vehicle is next stopped . according to the automatic transmission control unit 12 of the first embodiment , there is ensured a slow start with the second gear and stable running avoiding a rapid speed change in the case where a start and fine forward speed advance are repeated in a traffic jam with a shorter inter - vehicle distance . also in the case where an operator carefully steps on the acceleration pedal on a frozen road surface or a snow - covered road , a slow start with the second gear is ensured . since in these cases acceleration after a start is executed more inertially , there is no fear of unexpected powerful acceleration being produced even though output torque of the engine 11 and the idle speed are rapidly increased owing to on - off operation of an air conditioner , engine warming - up operation and other output controls . selection of such a second gear start is automatically executed by discriminating the changing rate of the throttle opening ( strength of stepping on the acceleration pedal by an operator ) so that there is no need of purposely performing setting and release by an operator as in a snow mode and so on . further , since a such second gear start function is realized with a slight alteration of a creep suppression control program for preventing the creep during the stoppage of the vehicle using the existing sensors and switches and the like as they are , there is no need of additionally providing specific sensors , setting switchs and instruments on the vehicle body , and there is further no need of altering wirings in the vehicle body including the automatic transmission control unit 12 . it should be noticed that the region a corresponds to the second control pattern and the second region of the present invention , and the region b corresponds to the first control pattern and the first region of the present invention . it should be further noticed that step 119 in the processing flow in fig5 corresponds to the control means for setting the predetermined low speed gear of the present invention , steps 111 , 112 , 120 to 122 , and 126 correspond to the control means for setting the high speed change gear of the present invention , steps 113 , 114 correspond to the means for switching the first control pattern to the second control pattern of the present invention , steps 116 to 118 to the return means of the present invention , steps 113 , 115 to the means for switching the second control pattern to the first control pattern , and steps 124 , 125 correspond to the continuation means of the present invention . fig6 is a flow chart illustrating the start control in a second embodiment . in the second embodiment , the constuction in fig1 the ordinary control in fig2 and the setting of the regions a and b in fig3 are commonly used , and the processing flow in fig5 is replaced for the processing flow in fig6 . as illustrated in fig6 in step 211 , control allowance conditions of the creep suppression control are determined . the rotary switch 16 is set to the forward advance mode whereby the creep suppression control is allowed when the vehicle speed v is v2 or less . otherwise , the creep suppression control is prohibited and the operation goes to step 221 . in step 221 , ordinary speed change control is executed . more specifically , provided the second gear or higher is set to the automatic transmission and the combination of the throttle opening and the vehicle speed falls in the allocation region for the first gear in fig2 shift - down to the first gear is executed . in step 212 , it is determined whether a set of signals to a plurality of the solenoids 17 of the automatic transmission 12 is corresponding to the first gear or not . with the first gear , since the down - shift to the first gear has been already completed even though the vehicle speed v is v2 or lower , the operation goes to step 221 where the ordinary speed change control is applied . otherwise , the operation goes to step 213 . it should be noticed that the fact that the control allowance conditions are met and the signals are for a gear other than the first gear indicates the state that the creep suppression control has been actually continued in the region a in fig3 ( or the region b in fig4 ) or the vehicle speed has been lowered to v2 or lower with the ordinary speed change control . in the second embodiment , the creep suppression control is applied even in the case , additionally to the time interval the operation escapes the region a ( or the region b ) after a start , where the vehicle speed is lowered because of the vehicle being caught up in a traffic jam during the running and hence acceleration and deceleration are repeated in the region a ( or region b ). in step 213 , there are estimated the number of times m of down - shift from the second gear to the first gear during past 10 seconds and the number of times n of the vehicle speed being lowered across the vehicle speed c . the vehicle speed c is a set value for determining conditions that wasteful shift - down to the first gear could be executed unless the shift - down to the first gear is executed , and is intermediate between a speed corresponding to the throttle opening th = 0 on the speed change line l2 in fig2 and a speed corresponding to the throttle opening th = 0 on the speed change line l4 . in step 214 , it is determined that the operation is under conditions where acceleration and deceleration are repeated in the low vehicle speed region provided the number m or the number n is 2 or more , and the operation unconditionally goes to step 220 where the creep suppression control is applied and meaningless shift - down to the first gear is prohibited . provided the number m or n is 1 or 0 , the operation goes to the next control region switching steps ( 215 to 217 ). the operation can be returned to the ordinary control provided an operator steps on the acceleration pedal in the acceleration state . in step 215 , it is determined whether the changing rate vth of the throttle opening th exceeds the set value ( a ) or not . if the set value ( a ) is exceeded , the operation goes to step 217 where it is determined whether the combination of the throttle opening th and the vehicle speed v falls within the region b in fig4 or not . if the rate vth is the set value ( a ) or less , the operation goes to step 216 where it is determined whether the combination of the throttle opening th and the vehicle speed v falls within the region a in fig3 or not . when it is determined in step 216 that the operation falls within the region a ( or within the region b in step 217 ), the operation goes to step 220 where the creep suppression control is applied and stable running is ensured avoiding a rapid speed change . in contrast , when it is determined in step 216 that the combination is outside the region a ( or region b in step 217 ), the operation basically goes to step 221 where the ordinary control is applied . however , even when the operation escapes from the region a ( or region b ) in an accelaration state , the second gear or more with the creep suppression control is continued until b second ( e . g ., 0 . 3 second ) elapses after the escape . hereby , there is prevented unnecessary shift - down to the first gear when the throttle opening th is varied up and down . more specifically , in step 218 , it is determined on the basis of stored data of the vehicle speed v estimated from an output of the vehicle speed sensor 18 whether the vehicle is in the acceleration state or not . with the acceleration state , it is determined that an operator strongly steps on the acceleration pedal to obtain powerful acceleration , and the operation goes to step 219 . in contrast , the state of the greater throttle opening in the deceleration state or in a constant speed running state means that an operator feels insufficient power because of the vehicle reaching an upward slope for example so that the operation is returned to the ordinary control through step 218 to exhibit powerful acceleration with the first gear . in step 219 , it is determined whether b second elapses after the operation escapes the region a ( or region b ) or not . if it is prior to the lapse of b second , the operation goes to step 220 where the speed change gear of the second gear or more with the creep suppression control is kept . after the lapse of b second , the operation goes to step 221 where the ordinary control is applied , and if the operation is in the allocation region for the first gear , shift - down to the first gear is executed . according to the start control of the second embodiment , the shift - down to the first gear is executed for the first time when the operation continuously escapes from the region a ( or region b ) for b second in the acceleration state so that there is eliminated meaningless repetition of the down - shift to the first gear when an operator unnecessarily varies the throttle opening up and down . more specifically , an output of the automatic transmission varies each time the speed change is executed to cause slight speed change shock and further to cause a response of the vehicle body to the stepping by an operator on the acceleration pedal to be changed . accordingly , driving characteristics and comfortabilities are improved and the running condition is also stabilized by eliminating the meaningless shift - down to the first gear . further , the creep suppression control is assumed to be applied , additionally to the time interval until the operation escapes the region a ( or region b ) after a start , also when the vehicle speed is lowered under the ordinary control and the operation enters the region a ( or region b ), and since the operation is returned to the ordinary control only by permitting an operator to step on the acceleration pedal in any case , acceleration performance and driving response in the low vehicle speed region are uniformed to prevent the operator to feel a sense of incompatibility due to the creep suppression control . further , under the conditions where the automobile is caught up in a traffic jam during the running , and hence acceleration and deceleration are repeated in the low vehicle speed region ; the shift - down to the first gear is prohibited until the repetition is interrupted to ensure the running with the stable vehicle speed , so that an inter - vehicle distance can be easily kept to improve the driving characteristics of an automobile installed with the automatic transmission . it should be noticed that step 221 in fig6 corresponds to the control means of the present invention for setting a predetermined low speed gear , step 220 to the control means of the present invention for setting the high speed gear , step 215 to the means of the present invention for switching the operation to the second control pattern and the means for switching the operation to the first control pattern , steps 216 and 217 to the continuation means of the present invention , steps 216 to 218 to the return means of the present invention , and step 219 corresponds to the return delay means of the present invention .