Why automakers are at a crossroads on diesel rescue

Checkpoints might become a familiar sight next year on the streets of Stuttgart, but police won't be looking for drugs or weapons. They will be searching for illegal Euro 5 diesels. As odd as it sounds, randomly stopping cars would likely be the only way without enacting a new law for authorities to determine if a vehicle's exhaust was clean enough to enter the city. This traffic-snarling scenario could become a reality for drivers should local authorities be ordered by courts to finally uphold a 7-year-old clean air target from the European Union.