Motorring 4 (O4) is a motorway ring road that runs from Ishøj to Ballerup.

In November 2003, a majority in the Folketing agreed on a traffic package, which meant that the drafting of a decision-making basis for expanding the motorway from 4 to 6 lanes had to be initiated.

[1] In July 2009, a significant part of the decision-making basis for a construction act was completed for approx.

4 km long stretch between Motorvejskrys Taastrup and the connecting facility between Motorring 4 and Frederikssund motorway.

Therefore, the expansion can be carried out by extension with tracks in the existing central rebate.