Being the nerd I am this is something I've thought about a lot. It feels like the Warp 5 speed limit is something that "should" have a lot of impact on the plot of the show but for some reason has NEVER been addressed properly.

Firstly lets break down the two parts of the Speed Limit as simply as we can:

1. All Federation Vessels MUST travel at no faster than Warp 5 - Unless given emergency clearance. We see this clearance given in a few episodes. This Speed Limit is in affect throughout ALL of Federation Space.

2. In areas of space in imminent danger of "space damage" due to warp fields, there was ban on all but the most essential travel.

The Speed Limit was initially introduced in TNG: Force of Nature (7x09). The Speed Limit was bought up again in TNG: The Pegasus (7x12) and TNG: Eye of the Beholder (7x18). Other than these episodes, however, the speed limit is never bought up again in either TNG or even DS9.

There was never an attempt on screen to explain what happened to the speed limit. I assume most people simply thought a magic fix was found. In my opinion I thing the problem arose from the speed limit being a "TNG" problem and well...TNG kinda ends after season 7.

Now there are several Beta-Canon sources that try to elaborate on the speed limit.

First is the Star Trek Voyager Season 1 Writer Bible released in 1994. The bible contains some interesting press release material. A part on the U.S.S. Voyager's engineering section states that the ships new warp drive system was more efficient than previous models and as such allowed the ship "to exceed the warp speed limit imposed in the Star Trek TNG episode 'Force of Nature', without polluting the space continuum". The Bible makes no reference to "Variable Pylons or Nacelles". This bible would have been released in the gap between TNG ending and VOY starting. This information about the speed limit is not repeated in any of VOYs other season bibles.

The next Beta-Canon source is Michael and Denise Okuda's "Star Trek Encyclopedia". Now here is where it gets confusing as the book seemingly contradicts itself a few times. The 1st edition released in 1994 suggests that Warp 5 became the "New normal cruising speed" after TNG: Force of Nature. This 1st edition was released shortly before TNG ended.

In 1999 a 3rd edition of the Encyclopedia was released with the new information that "The Starship Enterprise-D and other ships observed the “warp speed limit” for the remainder of Star Trek: The Next Generation. After that, it was assumed that Starfleet was able to develop a more “environmentally friendly” warp drive, so the speed limit was evidently lifted." (p.187). From this it would seem the authors were pretty certain the speed limit was dropped by the time TNG ends. In a different entry later on it states "A Temporary upper limit for warp speed travel was established in Force of Nature". One may interpret this wording as evidence the speed limit was always intended to be a temporary thing by the writers.

HOWEVER, the new edition also starts talking about the ever favorite "Nacelles". The entry on warp factor (p.555) states that "Later advances in Federation warp drive technology permitted the use of speeds exceeding warp 5. One of the first ships to be so equipped was the Intrepid- class U.S.S. Voyager, whose variable-geometry warp drive nacelles prevented damage to the subspace continuum". As such this supports the idea that the writers wanted to go into Voyager without any of that Speed Limit baggage and as such the engines/nacelles on certain ships are upgraded to negate this.

The Okudas elaborate on this by stating "This speed limit was abandoned a couple of years later when it was assumed that newer Federation starships (like the U.S.S. Voyager and the new Defiant) had improved, environmentally friendly warp drive systems that did not cause damage to the spatial continuum".

Now the question that is left unanswered is whether this implies the speed limit as a whole was dropped or whether the speed limit was dropped for Certain ships e.g. the U.S.S Voyager and Defiant.

Even MORE confusing is this information contradicts the earlier statement on page 187 that stated that the speed limit was lifted AFTER the end of TNG for ALL ships. (If the Okudas ever read this I'm sorry for nitpicking)

Finally we have the unpublished Voyager "Technical Manual" which states that the Variable Geometry Warp Nacelles on the U.S.S. Voyager "may no longer have a negative impact on habitable worlds, as established in TNG". This Manual was again published in 1994, likely in the gap between TNG ending and VOY starting. As such the stance of this manual is that the Speed Limit was still in affect by the time of Voyager, but ships like the U.S.S Voyager could bypass it with "Clean Nacelles". As such, this supports the information published in the Star Trek Encyclopedias (Mostly) and the Voyager Bible (Kinda).

For a while this was the final say on the topic until we reach Voyagers late season 7 episode "Renaissance Man" (7x24). Now as I haven't watched Voyager in a long long long time, I will just use the wiki as evidence. The Memory Alpha Entry on Variable geometry pylons states: "Renaissance Man)" however suggested that the warp drive of the Voyager still caused the cumulative damage. In the episode, members of the Hierarchy capture Captain Janeway and demand the warp core of the Voyager in exchange for her. The Doctor comes up with a lie for the crew of the Voyager, that they had entered R'Kaal space, a species of ecological extremists he had invented, who had supposedly outlawed warp travel in their space, because conventional warp engines damage subspace. When he claims this is the reason why Voyager has to surrender its warp core, the crew makes no effort to convince the R'Kaal that their warp drive is environmentally safe".

Many people use this episode as evidence that the speed limit was still in affect by the end of Voyager or at the very least that a fix hadn't been found yet. I've always found it weird that they waited until the PENULTIMATE episode of the show to bring this topic up again and to me screams of "Um guys I've ran out of ideas....hmm does anyone remember that whole thing about banning warp travel or something". Its possible the writers (Who only ever wrote a few episodes of Voyager) weren't aware of the implications of what they were talking about. (Wouldn't be the first time). In my opinion I always just figured that whatever fix to the warp drive they came up with, didn't actually 100% make the engines environmentally friendly, just heavily negated it.

An interesting note is that due to the lack of an actual on-screen explanation, Memory-Alpha basically thinks the speed limit is potentially in affect as of the most modern Star Trek Content. Which I find unlikely.

This last mention in the penultimate episode of Voyager was the last we heard of the speed limit for about 23 years until the Lower Decks episode "Caves" (4x08). This episode seems to suggest that the whole Warp fields being damaging to subspace was a massive conspiracy planted by the Vendorians. Or maybe not, its not very clear. So make of this what you will. Maybe this a way of the writers trying to explain away why the speed limit was dropped so quickly (Potentially after the end of TNG as other sources suggest). But who knows *Throws up arms*

I just wish the writers would write one or two lines and give me peace of mind but apparently that's too hard *Cries*.

In my personal opinion the Speed Limit was dropped for SOME reason between the end of TNG and about the first episode of VOY. Perhaps with the discovery of a fix to the issue, Starfleet reversed the ban and then started retrofitting older models of ships or phasing them out when they can. Perhaps at the same time they realised it was some weird Vendorian conspiracy (Maybe)

At the same time though, I think the areas of space most at risk of damage were likely left as restricted areas unless the ships traveling through them had one of the new engines upgrades.

I am not in the camp that believes that maybe one or two of the more modern ships in the Federation were given a fix and the rest of the fleet was left to languish at Warp 4.7-5 for the rest of eternity. To me thats just silly. Especially given that the Romulans, Cardassians and whoever else are BOUND to ignore it. Thus putting them at massive advantages even in peacetime.

But at this point I'm just tired of writing this thing and want to see what you guys think. I would like to see this as the last word on the whole Speed Limit topic as I believe I've pretty much gathered all possible information and laid it out.