In the shadow of the UTMB® and CCC®, the TDS® has earned a distinct reputation: the most technical race of the HOKA UTMB Mont-White® week. Shorter than the flagship event but noticeably rougher, it connects the Aosta Valley to Savoy across the Beaufortain. Here is everything you need to know before taking it on.
Key takeaways:
- 148 km and 9,300 m of positive elevation gain on the 2026 edition, from Courmayeur to Chamonix.
- A night start, at 23:50 on the Monday of race week.
- 44-hour and 55-minute cut-off time.
- 4 Running Stones and no lottery: entry operates on a first-come, first-served basis.
- Higher technicality than the UTMB®, across remote high-altitude sections.
TDS®: what the acronym means
TDS® stands for Sur les Traces des Ducs de Savoie (In the Footsteps of the Dukes of Savoy). The name refers to a historic alpine route linking the Aosta Valley and Savoy, two territories long united under the same realm. The race is a point-to-point journey crossing the border from Italy into France.
TDS® key figures
| Distance | 148 km, finish measured at 150.5 km |
| Positive elevation gain | 9,300 m |
| Elevation gain per kilometre | approx. 63 m |
| Effort-kilometre | approx. 240 |
| Start | Courmayeur (Italy), Monday at 23:50 |
| Finish | Chamonix (France) |
| Cut-off time | 44 hrs 55 mins |
| Running Stones | 4 required |
| Lottery | No, first-come, first-served |
| 2026 DNF rate | nearly 45% |
2026 stats recorded via official LiveTrail tracking. The route is tweaked each year, and the pre-race announced distance may vary slightly from the actual measured course.
The TDS® gains around 63 metres per kilometre, compared to 57 for the UTMB®. It is shorter, but steeper.
Course and key checkpoints
The course sets off from Courmayeur late in the evening and immediately tackles the heights of Val Veny, crossing Mont Favre and Lac Combal in the dead of night. The route then descends towards La Thuile, before dropping down to Bourg-Saint-Maurice around kilometre 51, marking the lowest point on the course.
Next comes the crux of the race: a long climb towards the Beaufortain, followed by the crossing of the massif via Cormet de Roselend and La Gittaz before reaching Beaufort. Technical terrain, high mountain exposure, very few bail-out points. This is where gaps are made.
The final section heads back into the Chamonix valley via Les Contamines-Montjoie and Les Houches, before the finish in the heart of Chamonix.
Intermediate cut-offs and aid station locations are published annually in the official roadbook on the TDS® page. Actual split times can be tracked on the event's LiveTrail tracking page.
Why is the TDS® considered tougher than the UTMB®?
Yet it is twenty-six kilometres shorter. Four key factors explain why:
- Terrain technicality. Narrow trails, scree fields, and cable-assisted sections in certain editions. You run less and power-hike more.
- Elevation gain per kilometre, higher than in the flagship race.
- Remoteness. The Beaufortain crossing features long stretches with no road access where self-sufficiency is paramount.
- Night start. In late August, roughly seven hours pass between the start and daybreak: the entire first section is tackled by headlamp, with temperatures frequently dipping near 0°C at mountain passes.
The 2026 results underline the difficulty: out of 1,290 starters, only 715 reached Chamonix, alongside 575 dropouts. A DNF rate of nearly 45%, battled through a night of cold rain. Full details are in our article on Rémy Brassac's victory at the 2026 TDS®.
How to register for the TDS®
The TDS® does not use a lottery, unlike the UTMB®, CCC®, and OCC®. Entry operates on a first-come, first-served basis when registrations open in January. You must, however, hold 4 Running Stones and a valid UTMB Index.
For a runner targeting race week in Chamonix without rolling the dice in the lottery for years, this is often the most direct route. Provided you are ready the day registration opens, as bibs sell out fast.
Details on how Running Stones and the UTMB Index work can be found in our dedicated guide: how many ITRA points or what Index for UTMB®. Registration procedures and general dates are detailed in how to register for UTMB®.
Gear: do not underestimate the race
The TDS® requires the organizer's mandatory gear, inspected at bib collection and along the route. Given the night start and high altitude, two items require particular attention:
- The waterproof hooded jacket complying with race regulations, meant to be worn, not just packed.
- Warm layers, as night-time pass crossings regularly see temperatures hover around 0°C.
Poles are permitted and used by virtually the entire field given the elevation profile. Check out the full checklist and our recommendations in our article on mandatory gear for the UTMB®.
Training for the TDS®
Training is broadly similar to any other mountain ultra, with one key difference: technical trail work must take priority. Being able to descend fast over scree and rugged trails pays far greater dividends here than a slight bump in VO2 max.
Our training guides cover all the essentials: how to prepare for an ultra-trail, training overload weekends, and hill training.
Frequently asked questions
What is the distance of the TDS®?
148 km with 9,300 m of positive elevation gain for the 2026 edition between Courmayeur and Chamonix, with the finish measured at 150.5 km on the official tracking. The course varies from year to year and may be modified mid-race if weather demands.
Is the TDS® harder than the UTMB®?
It is twenty-six kilometres shorter, but climbs more per kilometre and covers more isolated high-altitude sections. Its reputation comes from this technicality, not its raw length.
What is the DNF rate on the TDS®?
It is high and heavily weather-dependent. In 2026, out of 1,290 starters, 715 runners finished and 575 dropped out, representing nearly 45%.
Is there a lottery for the TDS®?
No. It is the only major race of the week operating on a first-come, first-served basis. You still need 4 Running Stones and a valid UTMB Index.
What is the cut-off time for the TDS®?
44 hours and 55 minutes, with intermediate cut-off times at main checkpoints published in the official roadbook.
Does the TDS® start during the day or at night?
At night, at 23:50 on the Monday of race week. In late August, daylight arrives roughly seven hours later, meaning the first section is run entirely by headlamp.
Find out more
- 2026 TDS®: Rémy Brassac's victory
- UTMB®: the race and the 2026 distances
- Mandatory gear
- How to register for the UTMB®
- The history of the UTMB®
Photo credits: Cordada Outdoor.
