Andrew Shovlin, Trackside Engineering Director :
We’ve had three useful days here in Bahrain and managed to make good progress understanding the W15. Compared to last year’s car, the feedback from the drivers is very different and more positive, which is encouraging. The team has worked hard to iron out the handling flaws that were integral to the W14, and it’s great that we seem to have put a number of those problems behind us.

Over the course of the test we’ve made good steps on our understanding of the car. The task of the next few days is to pick through the results and put together the best package to take into the race weekend. It’s never easy to make predictions on pace from testing, as all teams are quite effective at hiding their pace when they want to. It’s clear that we are in a much better position than 12 months ago though. We’ve got a busy few days ahead now making our final preparations for the season-opener, and we’re already looking forward to the race weekend and the season ahead.

Source and more info : Mercedes-AMG Petronas F1 Team