Sunday, the 12th of May, there is a running event – the Utrecht Marathon.
The event starts around 09:30 in the Uithof and the runners will come in the direction of the city center.
Due to this, the St. Catherine Cathedral may be difficult to reach between 10:30 and 15:00.
More info here: https://www.utrechtmarathon.com/
If you plan to come to the mass please plan with extra time to avoid any delays.