Update Jan 2022: The data presented here was a rough analysis of the of the Trans-European Alpine before it was hiked in 2019. The route has seen some changes since. A more accurate analysis can be made from present data in the TEAR overview and section pages, and is discussed in The Trans-European Alpine Route - Hike Across A Continent)
Original post follows:
Earlier this year we finished a 'first draft' gpx route for the TEAR, so lately I've been compiling some of the data for the total length and elevation gain/loss.
I'll compare the results below with the better known thru-hiking trails in the US - The Appalachian Trail, Pacific Crest Trail, and Continental Divide Trail.
Length
This one's easy. Even the longest of the big 3 US long-distance hiking trails, the Continental Divide Trail, comes in at only ~3,000 miles long. Most thru-hikes will also end up shorter than the official value due to the many alternates that are available for hikers. The Appalachian Trail (2,185 miles)* and the Pacific Crest Trail (2,669 miles)* are both shorter, but any of the 'triple crown' hikes are still massive undertakings for anyone attempting to hike the entire distances in one trip. At a current (lowball) estimate of 4,014 miles, the TEAR is considerably longer than all three. In fact, it's only slightly shorter than an AT Yo-Yo hike (End-to-End, and back).
Elevation
TEAR High Point: Theodulpass - 10,810ft TEAR Low Point: Cape Emine, Cape Finisterre - 0 ft (Sea Level) The TEAR reaches higher than the AT, but not as high as the PCT or CDT. However, more important than the elevation extremes are the regular gains and losses in elevation throughout the trail.
Elevation Change
The TEAR gains/loses 1,550,686 ft of elevation over 4,014 miles, averaging 386 ft/mi.**
That's...quite a bit.
Fun fact: That's the same total elevation gain/loss required to climb Everest 27 times from sea level. With our expected timeline of 7 months, that will average out to roughly one Everest summit and descent every week.
Here are the others for comparison: The Appalachian Trail gains/loses 917,760′ over 2185.3 mi (avg: 420 ft/mi) The Pacific Crest Trail gains/loses 824,370′ over 2668.8 mi (avg: 309 ft/mi). The Continental Divide Trail gains/loses 917,470′ over 3029.3 mi (avg: 303 ft/mi).***
The TEAR ends up ranking just below the AT in terms of average elevation change, which is a good indicator for the steepness/difficulty of a trail. The other factor is the type/quality of tread we'll be hiking.
Type of Trails Used
As for hard numbers, we know that 91% of the current route is on official hiking trail networks. Some of these trail networks will include roads, and some of the sections that are not part of trail networks will still include local walking paths.
For comparison, the PCT is basically a continuous single track with slopes that are gradual enough for horses to travel - a hiker's dream. The TEAR will be nothing like that. Most of the tracks through the mountains have existed for ages and will likely head straight up and down towards their targets like the AT. However, with a constantly changing mixture of trails, paths, country roads, and town streets, the TEAR will more closely resemble the CDT - but even that's probably a stretch. The PNT or Te Araroa will probably be better comparisons for those familiar with them, but it's really impossible to say before actually hiking the thing.
These last two comparisons don't rely on hard data, but they're interesting nonetheless.
Theme
Originally, the goal behind the TEAR was to create a hiking route that crossed an entire continent while keeping to the mountains as much as possible. In that sense it would be similar to PCT or CDT, which each take mountainous routes across an entire country. After studying the geography of Europe more closely it becomes apparent that it's actually much closer to the CDT philosophy than intended. As it's name implies, the CDT follows (quite closely) the continental divide of North America, taking you along the backbone of the continent which parts the waters east and west to the Pacific and Atlantic Oceans. For Europe, if you simply consider which areas drain north (to the Black Sea, North Sea, and Atlantic Ocean) and which drain south (to the Mediterranean Sea) you can create a similar divide.
The only time the route crosses a major drainage is the Rhone, after leaving the Alps. Surprisingly, the TEAR ended up behaving like a European version of the CDT in terms of it's overall geography.
Wilderness
While we don't expect to see any fellow TEAR hikers out there, Europe is densely populated and there will be no shortage of other people around. The trails and huts will likely be very busy during the summer months. The sense of remoteness that one might feel on the PCT or CDT may not exist in the same way on all sections of the TEAR, but it still promises to be a huge adventure through an unfamiliar land.
Notes
*Exact numbers vary from year to year due to trail changes, but these are close enough for rough comparisons
**The numbers are given in Imperial units for easier comparison with common AT/PCT/CDT data. ***Data referenced from Guthook