int selectedTypeLoko = 1;
SelectList typeLoko = new SelectList(db.TypeLokoes, "ID", "tlName", selectedTypeLoko);
ViewBag.TypeLoko = typeLoko;
SelectList numberLoko = new SelectList(db.NumberLokoes.Where(n=>n.tlID == selectedTypeLoko), "ID", "nlName");
ViewBag.NumberLoko = numberLoko;

public ActionResult GetNumberLoko(int ID)
        {
            return PartialView(db.NumberLokoes.Where(c => c.tlID == ID).ToList());
        }

$('#tlID').change(function()
        {
            // получаем выбранный id
            var ID = $(this).val();
            $.ajax({
                type: 'GET',
                url: '@Url.Action("GetNumberLoko")/' + ID,
                success: function (data) {

                    // заменяем содержимое присланным частичным представлением
                    $('#nlID').replaceWith(data);
                }
            });
        });

 public ActionResult GetNumberLoko(int tlID, int areaID)
        {
            return PartialView(db.NumberLokoes.Where(c => c.tlID == tlID && c.areaID==areaID).ToList());
        }

routes.MapRoute(
            name: "Loko",
            url: "{tlID}/{areaID}",
            defaults: new { controller = "Work", action = "GetNumberLoko" }
            );