Some took the ad blue route some took the erg route ad blue is better. But must new euro 6 trucks have both. The new daf has both as ad blue only works as the exhaust system gets up to temp. So the egr is there to reduce emissions until the exhaust is up to temp. The egr also heats the engine and allows the exhaust system to get up to temp along with a veritable vain turbo and injectior that doses fuel in to the exhaust. Once up to temp and using the ad blue system the egr helps cool the cylinder temp. The emissions system on a truck is fooking complicated now