Or may be they haven't finished the improvement work, from the MSV website:
Oulton Park owner MSV has carried out a programme of safety improvements over the winter, with increased run-off at Island Bend amongst changes that will be completed in time for the 2016 season.
The venue maintenance team, led by Circuit Manager Simon Bonser, braved the recent spell of wet weather to replace the current earth bank that ran along the spine between Shell Oils and Britten's corners with Armco. In addition, run-off areas at Island Bend and the Shell Oils Corner have been increased, with the gravel bed on the inside of Shell moved further back towards Island Bend, increasing the run off area available.
The work will be completed on time to ensure that Oulton Park's 2016 racing schedule won't not be disrupted, however trackdays will run on the Island circuit until March.