Many infinite runners scroll the road rather than move the player forwards on the road to make the road truly infinite. You can do this with 2 alternating game objects.

public GameObject[] RoadPieces = new GameObject[2];
const float RoadLength = 100f; //length of roads

const float RoadSpeed = 5f; //speed to scroll roads at
void Update ()
{
    foreach (GameObject road in RoadPieces)
    {
        Vector3 newRoadPos = road.transform.position;
        newRoadPos.z -= RoadSpeed * Time.deltaTime;
        if (newRoadPos.z &lt; -RoadLength / 2)
        {
            newRoadPos.z += RoadLength;
        }
        road.transform.position = newRoadPos;
    }
}


Just space the roads out correctly in the beginning, and this'll scroll them forever.

How do I make an endless road in Unity?
in this funciton when i use firebug i get "syntaxerror: missing ; before statement on the var url line.

    function makeRequest(){
                 var url= "contr_entry_pkg.sales_center_dropdown?&amp;pnSalesCenterID=document.getElementById("pnSalesCenterID").value +&amp;pvCurrCd='||CURRDEF||'";
                ajaxReq = (window.XMLHttpRequest)? new XMLHttpRequest() : new ActiveXObject("MSXML2.XMLHTTP")

                ajaxReq.open("POST",url ,true);
                ajaxReq.onreadystatechange =currencychange;         
                ajaxReq.send()         
        } 

