Keep your speed up!

[Innocuous Fox]

Another issue (and this is across airports but is REALLY an issue at SFO) is that aircraft don't keep any speed up while on the runway heading to a taxiway. In the case of SFO, this means that they creep through the center intersection.

The reason for the necessity at SFO is that you do not want RJs to exit 28L prior to the runway interesection (since that means they have to use F westbound and you need F for 28L heavy departures). Therefore, standard procedure is to tell them to exit at J or E. However, if you do that, they slow to 30kts as soon as they can and then slowly taxi all the way to the exit point. Because of how SFO departure traffic on the 1s has to be timed to shoot the gap on 28 arrivals, it quickly becomes prohibitive because arrivals on 28 end up blocking the intersection.

The fix to this is simple. If aircraft are either assigned a taxiway to exit on or know that the next available exit is further down the runway (BOS is notorious for this), instead of slowing to their taxi speed immediately, they need to keep their speed up somewhat until they reach a point where they HAVE to slow down to exit in time.

It's the same as how, when driving a car, we don't slow down when the light way in front of us changes to red. We slow SOME but keep moving until we are close enough that we have to slow down in time to stop. Only slow when you have to in order to exit.

[stealth89]

What is SFO?

[Innocuous Fox]

o_O

San Francisco

[stealth89]

Oh

[Innocuous Fox]

Yep... after trying and trying using the normal real life traffic patterns at SFO, it is pretty much unusable because it takes forever for the aircraft to exit the runway. They actually slow down to 20kts and creep through the intersection.

Very much like the "I will always stop upon exiting the runway, even if I have been told to taxi" problem, this isn't remotely how real aircraft operate. The thing is, these are likely a 1 or 2 line change in the programming. (I know, I do game AI for a living.) They're not hard fixes. Unfortunately, until they ARE fixed, using those airports is pretty much either broken or a frustrating experience.

[76561198805185114]

Hello,

We will look into this. Possibly not a bug, but a game limitation.

Ariel

[Innocuous Fox]

I know it isn't a bug -- that it IS a game issue. This is specificallly programmed in to the code. The pseudo-code for aircraft is this:

* Upon landing, slow using the aircraft's specified deceleration rate until you reach the taxi speed (~20kts)
* Continue at taxi speed until you reach your next turn (in this case, the exit taxiway)

Instead, all you have to do is decelerate to an intermediate rate (e.g. 60kts) for a period of time until you reach a point a certain distance away from the exit, then continue deceleration to 20kts for exit (or use a higher number for a high speed exit... that's why those exist).

Another method is to linearly interpolate from your current speed to the exit speed based on the remaining distance to that exit. That will create a smooth deceleration over that time and still guarantee being at the exit speed when you arrive at it.

Both of these methods have the advantage that, if there is a great space between the exits or the controller requests an exit further down the the runway (for taxi purposes), that the aircraft will keep the speed up for a longer period of time and not linger down the runway at 20kts. This is common practice for ATC but is prohibitively unavailable in this simulation (with the aforementioned results).

As I mentioned in a thread a few months ago, the "always stop on exiting runway" issue is another simple programming fix. You currently request a gate and taxi route path AFTER leaving the runway and coming to a complete stop -- even if the taxi routing has been given previously (e.g. while on the runway). Instead of that, rework the code by placing the gate assignment and taxi path request the moment the ATC gives the taxi command. That path can then be generated while the aircraft is continuing it's roll and can then proceed along that path (without stopping) upon exiting the runway. It's only a few lines of change -- largely just changing where the path request happens and removing the "stop" command after exit (unless a path doesn't exist -- in which case a stop is just fine).

Again, I do game AI constuling and contract work for game studios around the world. If you would like, I will sign and NDA. Give me access to your codebase and I will fix it (and many other bugs you have).

[FeelThereDev]

Thank you for your offer however if you are working in the game industry I'm sure you know it sounds good on a forum but it is absolutely not the way game companies operate.

The pathfinding and the whole AI behind the ground traffic is much more complex and totally different from the example above so we think the best is if we continue working on it ourselves.

We will see what can we do about it however it's also possible this will make the next version of Tower.

Thank you

Vic

[Innocuous Fox]

I apologize if I offended, but as I mentioned I do AI consulting and contract work. I'm pulled in to work for game studios as a hired gun all the time. Many game companies DO operate this way. That's how I make my living. :-)

And yes, I know that the ground traffic pathfinding is far more complex than illustrated. I was focussing on the specific issue. However, the fact remains that there are some very simple components of your simulation that are based on unrealistic behaviors which, in turn, break entire airports from working. (I've encountered the "taxi speed on the runway" problem to a game-breaking extent on SFO, BOS, JFK.) It's not a hard fix. Neither is the "stopping upon exiting the runway" issue. Or at least they shouldn't be.

Anyway, I love your product, but it disappoints me greatly that small bugs like this need to wait for a new version of a game.

[Aviato Aviator]

This is a huge issue for me as well. The aircraft slow down to 30 or 20 knots by Taxiway L and crawl through 01L/R. If I am using 01L/R for departures and 28L/R for landings, there are no departures since the aircraft barely get off the taxiway before the next one is landing. This causes a huge queue for departures during the busy periods.

[Allsop4]

I agree that this needs to be addressed. My only solution is to pull the Traffic Density slider down a bit. This creates gaps so that I can get my departures off.

[mjbhgrampy]

Not necessarily the solution, but may help. At a bare minimum, an interesting read.

https://forum.simflight.com/topic/85171-tower3d-pro-anatomy-of-a-ksfo-landing/