Complex sentence: The bridge is a concrete beam bridge completed in 1994 which forms part of the Haltwhistle bypass and allowed the road through Haltwhistle to be detrunked at that time.
Split into simpler sentences: The bridge is a concrete beam bridge, which forms part of the Haltwhistle bypass and which was completed in 1994. The creation of the bypass allowed the road through Haltwhistle to be detrunked at that time.