Here’s what’s going on:
Rideable Vehicles declares early on that “The stand up before going rule is not listed in any rulebook.” The stand up before going rule (part of the Standard Rules) is the one that makes you automatically get off a barrel before you move. It looks like this:
Check an actor going when the actor is on a supporter (called the chaise)
(this is the stand up before going rule):
if the actor is the player:
say "(first getting off [the chaise])[command clarification break]" (A);
silently try the actor exiting.
(The “(A)” here makes it possible to amend the default response by changing the “stand up before going rule response (A)” but we’re not going to do that so let’s ignore it.)
Rideable Vehicles doesn’t like this rule, because rideable vehicles are a subset of supporters, and we don’t want you to automatically dismount your bicycle when you try to ride it somewhere.
An interesting thing happens when we plug this rule back in, though. Let’s say your game looks basically like this:
Include Rideable Vehicles by Graham Nelson.
Svalbard is a room.
The reindeer is a rideable animal in Svalbard.
The barrel is an enterable supporter in Svalbard.
Nordpolen is north of Svalbard.
And we add the rule that Rideable Vehicles removed:
Check an actor going when the actor is on a supporter (called the chaise)
(this is the new stand up before going rule):
if the actor is the player:
say "(first getting off [the chaise])[command clarification break]";
silently try the actor exiting;
(Notice that this is “the new stand up before going rule,” so the compiler will include it, even though “Include Rideable Vehicles…” makes the compiler ignore the original stand up before going rule.)
The resulting game ends up playing like this:
Svalbard
You can see a reindeer and a barrel here.
>mount reindeer
You mount the reindeer.
>n
Nordpolen (on the reindeer)
>s
Svalbard (on the reindeer)
You can see a barrel here.
>dismount
You dismount the reindeer.
Svalbard
You can see a reindeer and a barrel here.
>enter barrel
You get onto the barrel.
>n
(first getting off the barrel)
Nordpolen
The new stand up before going rule correctly has us get off the barrel before leaving, but it doesn’t affect us if we’re riding the reindeer—because rideable animals are not technically supporters.
And things seem to be working just fine! So simply adding this “new stand up before going rule” (which is the same as the old stand up before going rule!) will solve your problem…
UNLESS you also plan to have non-animal rideable vehicles in your game! If we do that:
The bicycle is a rideable vehicle in Svalbard.
Then we get this:
Svalbard
You can see a reindeer, a barrel and a bicycle here.
>mount bicycle
You mount the bicycle.
>n
(first getting off the bicycle)
Svalbard
You can see a reindeer and a barrel here.
Which is of course the behavior that Mr. Nelson was trying to avoid when he unlisted the stand up before going rule. Actually, this does something really bizarre: The bicycle travels north without you—notice it’s no longer in Svalbard! I HAVE NO IDEA WHY THIS HAPPENS but it doesn’t matter, we’re gonna fix it.
As near as I can tell, all we need to do is to modify our “new stand up before going rule” so that it doesn’t apply to rideable vehicles. That is, we include the condition “if the chaise is not a rideable vehicle” like this:
Check an actor going when the actor is on a supporter (called the chaise)
(this is the new stand up before going rule):
if the chaise is not a rideable vehicle:
if the actor is the player:
say "(first getting off [the chaise])[command clarification break]";
silently try the actor exiting;
And now everything works perfectly—I can ride a bicycle, I can ride a reindeer, and I can’t ride a barrel. So really, hopefully, the above rule should be the only thing you need to add to make Rideable Vehicles behave.
(The fact that the original Rideable Vehicles extension didn’t handle it this way makes me wonder if perhaps this way has some undesirable consequences that I didn’t predict…but it’s probably fine.)