If you are familiar with FH4, then you will know the score with this achievement. Very straight forward.
There is only 5 Trailblazer events in the LEGO Valley but these are the most tricky of all the '3 star' events. I found I was getting 2 stars on my first few runs, but after plotting a better course and some rewind button action, 3 stars was in grasp. I used a tuned LEGO McLaren Senna, but many other vehicles with a good top speed & handling will work.
Festival Rush - 25 seconds remaining
City Approach - 25 seconds remaining
Cross City Charge - 25 seconds remaining
Desert Escape - 35 seconds remaining
Dunes Run - 20 seconds remaining