On this page of our guide to Batman: Arkham Knight you will find a walkthrough to the ninth trial set by the Riddler. Another time trial race and puzzle with keys await you.
The ninth Riddler trial takes place in the tunnels under the Ranelagh Ferry Terminal. Reach the garage gate and take the elevator down. Here, you will have to race three time trials that are much more difficult than the previous ones.
The first and the second race are quite similar to each other and in both cases you will have to use the Riddler blockade to manipulate the elements of the surroundings. You need to know that not all of the obstacles can be dealt with in this way. The first section of the route is definitely more difficult and it assumes that you take a long wall-drive along the right wall. You need to make sure that you remove the obstacles and not lose too much speed, or you will fall off the wall. Apart from that, the last section is quite demanding, where you ride over the left wall, for a change. In this case, make sure that you remove the obstacles at the last possible moment, and only when the batmobile is in a safe position (i.e. when it is safe from being destroyed by an extending obstacle).
Unfortunately, the third time trial is much more difficult, because the Riddler himself takes control of the obstacles, which makes it impossible to use the blockade. At the beginning of the course, take a slalom ride, drive through the gates when it is safe (if necessary, use the charger). After you get to the vertical right wall, you need to perform a slalom ride also. Additionally, make sure that you pass by the right obstacle without losing speed, because you will have to take a jump over operating mechanisms, after you get off the wall.
Towards the end, ride over the left wall again. Also in this time, slaloming is required. Try to be highly precise and activate the charger is short blasts, as soon as you notice the batmobile losing speed too fast.
After you complete all three time trials, stop the batmobile by the interactive pressure plate and walk onto it, as Batman. Analyze the readings of the panel and, after you switch to Catwoman, approach the correct capsule with the key inside (the above screenshot). However, this is not it, yet. There is still one more trial for you to do. Listen to Riddler and return to the surface as Batman.