Simple Lightning select component with two buttons. 
Expected output- Both drop-down(select component) and two buttons to be in center and on same line
Output - Both drop-down(select component) and two buttons to be in center and on different line

Can anyone tell me where I am wrong?
Thanks in advance 

<aura:component implements="flexipage:availableForRecordHome,force:hasRecordId" >
  <aura:attribute name="carTypes" type="String[]" default="Sport Car, Luxury Car, Van"/>
  <aura:attribute name="searchbuttonlabel" type="String" default="Search"></aura:attribute>
  <aura:attribute name="newbuttonlabel" type="String" default="New Button"></aura:attribute>
    <lightning:layout horizontalAlign="center">
         <lightning:layoutItem padding ="around-medium">
              <lightning:select name="selectItem" aura:id="carType" label="Select Type of Car" variant="label-hidden" value=" " >
                   <option value="" text="Select Type of Car"></option>
                <aura:iteration items="{!v.carTypes}" var="carType">
                       <option text="{!carType}"></option>
                </aura:iteration>                                 
               </lightning:select>
        </lightning:layoutItem>
        
        <lightning:layoutItem padding ="around-medium">
            <lightning:button label="{!v.searchbuttonlabel}" variant="Brand"/>
            <lightning:button label="{!v.newbuttonlabel}" variant="Neutral"/>
        </lightning:layoutItem>                    
    </lightning:layout>        
</aura:component>