Roebling Road is a 2.02 mile road course with 9 official turns.
The track is mostly flat, however turn 6 in somewhat downhill, turn 7 is the same amount uphill, and the pavement has a crown throughout most of the lap.
The lap consists exclusively of medium to high speed sweepers. There is not much variety going on at this track, but driving it fast is nonetheless quite challenging, because the car is constantly in high speed transitions.
Roebling Road is like Lime Rock turn 1 or NJMP Lightning turn 3 duplicated over and over to cover the entire lap. Although the track map looks similar to that of Thompson Speedway, these two tracks are very different owing to elevation changes and banking at Thompson.
When learning the track it is a good idea to approach corner combinations (turns 1-2, 3, 4, 5, 6-7 and 8-9) as exit speed sweepers, aiming for a decently fast entry with a conservatively late apex and early power application. The corners can generally be safely entered on the inside half of the pavement without giving up too much speed.
Entries into turns 4 and 6 are more slippery than others.
Apex and exit curbs are all usable, and flat except for turn 9 exit which has several dips.
Turn By Turn
The entry half of the turns 1-2 complex, turn 1 is a very fast decreasing radius right sweeper. It is very similar to Lime Rock turn 1, has some resemblance to Summit Point Main turn 5 and the middle of the corner drives like NJMP Lightning turn 4 with a downshift under light deceleration.
As turn 1 sits between the main straight and the tighter and slower turn 2, it is squarely an entry speed corner. The goal in turn 1 is to brake as late as possible without losing the car between turns 1 and 2. The fastest line will perform much of the braking in a diagonal from the left edge of the track toward the apex of turn 1. Low power cars like Miatas can brake at the 2 marker, with high power cars starting potentially at the 4 or 5 markers.
Turn 1 rewards a stable car and high amounts of grip.
Most cars would be somewhere left of center at the turn in point for turn 2, hence the line through turn 1 would end maybe 2/3 or 3/4 track left maybe 2/3 of the way between the apexes of turns 1 and 2. Tracking out all the way left is risky as that leaves no runoff room, although in the wet it can work well due to slower speeds overall. Similarly cars may miss the apex of turn 1 to flatten the approach into turn 2.
The exit half of the turns 1-2 complex, turn 2 is a slower right sweeper. The apex is blind, making turn 2 primarily about vision and consistency. Turn in for turn 2 should be somewhat left of track center line. Depending on a car's grip level a lift may be needed to rotate the car into turn 2 or the car may continue on the same arc it had through turn 1.
Exit curbing is very usable, including in the wet.
A very fast left sweeper, this turn is all about vision. It is so tempting to lift or brake there, depending on the car and conditions, and just about always the car can carry more speed there if the driver has the courage for it.
In the dry aiming to put the left front tire at the left side curb past the apex of turn 3 is a good way to set up for braking into turn 4. In the wet there tend to be puddles of water on the right side of the track going into turn 3, which compromises the line somewhat. Staying on the left half of the track throughout turn 3 in the wet tends to offer more grip than transitioning from the right side to the left side.
This turn is a bit tricky because its entry is rather slippery, and becomes more so the deeper a car goes in and the more steering angle is applied. In the dry I would recommend turning in early and not more than 2/3 track left for lower power cars. High power cars will not fit into the exit with an early turn in and would probably have to run a more traditional line through turn 4.
In the wet the turn remains slippery with puddles and slick spots scattered throughout the entry. The best rain line is generally to avoid standing water, or to just touch it with the right side tires.
The entry becomes more slippery deeper into the turn. This turn calls for an earlier entry than one might expect. Hugging the inside edge of the track works well.
The slowest turn of the track, turn 5 is closest to a corner (as opposed to a sweeper) at Roebling Road. Of course it still demands almost a 180 degree change in direction which makes it anything but easy to drive fast.
Vehicle grip level and surface conditions alter the line in turn 5 dramatically. A Miata on R compounds can turn in from the middle of the outside curb and use about the curb's length for braking prior to that. The same miata on street tires would turn in a couple of feet past the end of the curb and use one and a half curb lengths for braking.
In the wet the turn in points get later and the braking distances get longer. To complicate the matters there is a lake forming at the outside half of the track right where the wet turn in point would be, forcing the cars to turn in early even in wet conditions. A good compromise can be to forego the outside half of the pavement on entry and turn in roughly where the lake starts from mid track.
The exit from turn 5 is easy in the dry and complicated by a lake forming around the apex in the wet. Regardless of conditions, full track width should be used at the exit.
A right sweeper with a downhill entry. Similarly to turn 4 the entry becomes more slippery the deeper and sharper it is, although turning in early tends to wash the car out around the midpoint between turns 6 and 7. An entry roughly at the center track is best in the dry I think. The key in this corner is to turn in late enough to get on throttle and be able to stay on it through turn 7 exit but not late enough to lose the rear end on the entry.
The line in the wet becomes more traditional with the car going deeper and staying on the left half of the pavement. There are several lakes forming throughout the turn hence the fastest wet line is often the one bypassing the lakes.
If turn 6 is performed correctly, turn 7 is a non-event. An early entry in turn 6 typically results in the car running out of track in turn 7.
Turn 7 goes uphill to get back the elevation that turn 6 lost going downhill. The turn in point for turn 7 is still downhill though hence turn 7 drives somewhat like a late apex.
Turn 7 has a usable exit curb. If you hit the rumble strips around the paved part of the curb you are probably on the right line.
These two turns really drive as a single corner. In low power cars in the dry this combination is taken under full throttle, aiming right front tires to just miss the inside curb separating the track from pit entry. Exit curb has several dips in it, they can claim cars not straightening the wheel as they approach the outside edge of the pavement but at least for lower power cars the curb can be used under full throttle without any drama.
In the wet the car can wash out mid turn, hence aiming to stay on the right side of the track throughout the entire turn 8 and entry into turn 9 (up until the pit entry splits off, at least) can be a good idea. There is water accumulating around the apex of turn 9, putting the inside wheels on the inside of that water if possible aims the car rather well at the exit of turn 9 in the wet.