Complex sentence: There was no requirement in Europe for headlamps of standardised size or shape, as long as the lamps met the engineering and performance requirements contained in the applicable European safety standards.
Split into simpler sentences: There was no requirement in Europe for headlamps of standardised size or shape. Automakers were free to design their lamps to whatever shapes and sizes they wished, as long as the lamps met the engineering and performance requirements contained in the applicable European safety standards.