1. The cost of the upgrade isn't recovered fast enough.
2. The deadline to make the switch is still 17 months away.
A heavy truck that complies with Euro 4 emissions rules, which take effect Oct. 1, 2006, costs about 5,500 euros more than a truck that meets the current Euro 3 rules.
According to a survey by the Federal Bureau of Motor Vehicles and Drivers, 98.5 percent of heavy trucks registered in Germany comply with Euro 3.
There are some truck companies that are making the switch now. Mercedes-Benz received about 3,000 orders in the first quarter for low-emissions versions of its Actros series of heavy trucks. The trucks offer selective catalytic reduction exhaust after-treatment.
German truckmaker MAN has taken a different route to reduce emissions. The Munich-based company reduces NOx through engine modifications, cuts particulates using a particulate matter catalyst by Emitec and also employs an exhaust gas recirculation system. The disadvantage is that the technology is only available for engines with 350 hp or more.
A version of the system for MAN trucks with between 150 hp and 240 hp will be introduced by the beginning of 2006.
Swedish truckmaker Scania uses exhaust gas recirculation only to meet Euro 4 and Euro 5 norms with its six-cylinder engines. The disadvantage is that this technology includes an additional cooling system that robs engine of performance and increases fuel consumption.
A number of governments are giving discounts to trucks that make the upgrade prior to the Euro 4 and 5 deadlines. In Germany, the highway toll is reduced by 1 cent per kilometer for Euro 4-compliant trucks and 2 cents per kilometer for trucks that meet Euro 5 standards.
For many, that is not enough to make the extra investment.
"With a 40-ton truck with an average road performance of 180,000 kilometers a year, about 80 percent of the distance would need to be driven on German highways for the additional cost to amortize within two years," said Werner Struck, an engineer with Dekra, a testing specialist based in Stuttgart.