Effect on Noise Annoyance by Widening Danish Highway

Motorway M3 in Copenhagen has been widened from two to three lanes on seventeen kilometers. It is an urban highway passing through densely populated residential areas. Before the widening, there were 1.5 - 2.0 meter high noise barriers along the motorway. As a part of the widening nearly eighteen kilometers of four meter noise barriers were constructed together with noise reducing road pavements and facade insulation. Noise mapping showed that in the existing situation, six thousand three hundred dwellings were exposed to road traffic noise over 55 dB (LAeq,24h). With the new noise abatement only two thousand two hundred dwellings will be exposed to noise levels over 55 dB. An investigation on annoyance due to road traffic noise was carried out by the Danish Road Directorate/Danish Road Institute as a pre and post-study in six residential areas covering twelve hundred dwellings. The results showed that there has been an improvement in the perceived noise annoyance. The total percentage of very and extremely annoyed respondents decreased from 37 % to 16 %. The percentage of moderately annoyed was almost constant with 30 % and 27 % respectively. Finally, the total percentage of slightly annoyed and not at all annoyed increased from 33 % to 57 % from the pre to the post study.