;WITH cte(car_Id, traceXML) AS
(
SELECT car_Id, CAST('<A>' + REPLACE(trace, ';', '</A><A>') + '</A>' AS XML)
FROM dbo.cars
), cte2 AS
(
SELECT car_Id, trace, NTILE(4) OVER(ORDER BY (SELECT 1)) AS grId
FROM cte
CROSS APPLY (SELECT Tbl.Col.value('.', 'nvarchar(250)') AS trace
FROM traceXML.nodes('/A') Tbl(Col)) AS List
), cte3 AS
(
SELECT DISTINCT a.car_Id,(
SELECT ISNULL(b.trace, '') + ';'
FROM cte2 b
WHERE b.grId = a.grId
FOR XML PATH('')) AS trace
FROM cte2 a
)
SELECT DISTINCT a.car_Id,(
SELECT ISNULL(b.trace, '')
FROM cte3 b
WHERE b.car_Id = a.car_Id
FOR XML PATH('')) AS trace
FROM cte3 a
Demo på SQLFiddle