E-code (short for ECE specification) lenses are an international standard in western Europe. Their main feature is that they focus a higher percentage of light on the road surface, with a hard horizontal cutoff tapering to a distinctive upward slant to the right (except in UK, where it's left). This slant highlights signs, roadside obstacles, and curb lines. Because E-codes focus their light more efficiently, the result is experienced as a more brightly lit ride. A hard horizontal cutoff protects oncoming drivers from the glare of the higher output lamps you can get in Europe (and only in Europe). The high beam specification is tailored toward autobahn/autostrade type driving: pushing the light far out ahead of the car, not too much spread to the sides.

US DOT lenses, on the other hand, are primarily a fuzzy glow. A lot of light is directed upward in every direction, ostensibly for the purpose of illuminating overhead signs. (Funny, the overhead signs are lit just as brightly by my E-codes.)

For an excellent write-up, check out the FAQ's at Daniel Stern's informative site: http://lighting.mbz.org/faq/
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)