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⏵ Course guide · Flat, fast, world-record trail

Tunnel Hill 100 Course Guide

Tunnel Hill 100 runs its 100 mile, 100K, and 50 mile races on the smooth, crushed-limestone Tunnel Hill State Trail out of Vienna, Illinois, a flat course fast enough that five world records have fallen here. I will walk you through the loop structure and the strict time limits first, then give you a pacing and fueling plan for a long, flat effort, plus free tools to dial in your own numbers.

⏵ At a glance

Tunnel Hill 100 quick facts

Date
Saturday, November 14, 2026, 7:00 AM CST
Location
Vienna City Park, Vienna, Illinois, on the Tunnel Hill State Trail
Distances
100 Mile, 100K, 50 Mile, and a Marathon
Course
Crushed-limestone rail trail; 50-mile loop (out to the Wetlands Center, north to a turnaround, back to start/finish) repeated for the 100; 100K adds a further out-and-back south
The tunnel
100K and 50-mile runners pass through the historic tunnel twice; 100-milers pass through it four times
Time limit
30 hours for the 100 Mile, 100K, and 50 Mile, strictly enforced with no grace period; 100-milers must begin their second 50 in under 15 hours
After dark
The Tunnel Hill State Trail closes to non-race traffic at dark; a runner pulled after dark still earns a 50-mile buckle if they reached that point
2026 distinction
2026 USATF 50-Mile National Championship
World records set here
5, including Zach Bitter's 12:08:36 100-mile world's best off-road (2018) and the current 100-mile and 50-mile women's world records, both set in 2025
Organizer
Durbin Race Management, race director Steve Durbin

These facts come from the official Durbin Race Management site and the UltraSignup registration page. Check the current year details, cutoffs, and registration window before you commit. Race logistics change year to year.

The course: a flat rail trail, run in repeating loops

Every distance shares the same 50-mile course structure. What changes is how many times you run it, and how many times you pass through the tunnel that gives the race its name.

The 50-mile loop: south to the Wetlands Center, north, and back

The course starts at Vienna City Park and heads south on the crushed-limestone Tunnel Hill State Trail to the Wetlands Center at 13.1094 miles, exactly a half marathon, then turns back north for a much longer stretch to a certified turnaround before returning to the start/finish. That full out-and-back sequence covers 50 miles. The 50-mile race runs it once, the 100K adds a further out-and-back to the south, and the 100-mile race repeats the entire 50-mile course a second time.

Through the tunnel, twice or four times

Because the course structure repeats, 100K and 50-mile runners pass through the trail's namesake tunnel twice, and 100-mile runners pass through it four times. The surface throughout is smooth, crushed limestone over a dirt bed, tree-lined for most of the route, which keeps footing simple even in the dark.

World records, and a 2026 USATF championship

Five world records have been set on this course, including Zach Bitter's 12:08:36 men's 100-mile world's best off-road in 2018, and both the women's 100-mile and 50-mile world records, set in 2025. Zach Bitter is confirmed as the 2026 guest speaker. The race also carries 2026 USATF 50-Mile National Championship status, so expect a genuinely competitive field mixed in with runners chasing their own personal goals.

Pacing strategy for a strict, no-grace-period cutoff

The flat terrain removes elevation change from the equation, but the 30-hour limit and the requirement to start your second 50 in under 15 hours make pacing discipline the real test here.

Respect the 15-hour split, not just the 30-hour finish

If you are running the 100 mile, the requirement to begin your second 50-mile loop within 15 hours is a real checkpoint, not a soft target. A finish-time projection built around your actual training paces on flat terrain, checked against that 15-hour split, tells you early whether your first 50 left you enough room, rather than finding out at the cutoff itself.

Do not chase the flat terrain's easy early feel

A smooth, flat rail trail tempts you to run faster than your fitness supports simply because the effort feels easier than trail running. A steady, even pace built around your real fitness protects your legs for the back half of a 50, 100K, or 100-mile effort, especially once the Tunnel Hill State Trail closes at dark and you are racing the clock as much as the distance.

⏵ Free tools to pace this course

Fueling strategy for a long, flat November effort

A mid-November start in southern Illinois means daytime running and overnight running for 100-mile runners, and your fueling plan should account for both.

Carbs: steady across a long, flat effort

Aim for roughly 60 to 90 grams of carbohydrate per hour, and use the aid stations along the crushed-limestone trail for regular resupply. A flat course keeps your effort more consistent than a mountain 100, so an even fueling rhythm tends to work well here.

Layer for overnight miles on the 100

If you are running the 100 mile, part of your race happens after dark, when the Tunnel Hill State Trail itself closes to non-race traffic. Mid-November nights in southern Illinois can turn cool, so pack layers alongside your fueling plan rather than relying on daytime temperatures for your whole race.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a long day and night on a flat rail trail with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

⏵ Train for it with Summit Line

Get a race-day plan built around YOUR fitness, this exact flat, repeating-loop course profile, and your projected splits at the 15-hour and 30-hour checkpoints. Summit Line reads your real training, builds a plan for a long flat effort, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

Tunnel Hill 100 FAQ

How hard is Tunnel Hill 100?

It is flat and fast by ultra standards, a smooth crushed-limestone rail trail with none of the technical footing or elevation change of a mountain 100. That is exactly why it draws a stacked field: five world records have fallen on this course, including Zach Bitter's 12:08:36 men's 100-mile world's best off-road in 2018 and the current women's 100-mile and 50-mile world records, both set in 2025. The difficulty here is pacing discipline over a long, repetitive course and the mental grind of an out-and-back-style layout you will see multiple times.

What makes the Tunnel Hill 100 course structure unusual?

The 50-mile course runs south from Vienna City Park to the Wetlands Center at 13.1094 miles, turns north for a longer stretch to a turnaround, then returns to the start/finish, and the 100-mile race repeats that 50-mile loop twice. The 100K adds a further out-and-back to the south. Because of this structure, 100K and 50-mile runners pass through the trail's namesake tunnel twice, and 100-milers pass through it four times.

What are the cutoff times for Tunnel Hill 100?

The 100 Mile, 100K, and 50 Mile all share a 30-hour time limit, strictly enforced with no grace period. 100-mile runners must begin their second 50-mile loop in under 15 hours. The Tunnel Hill State Trail itself closes to non-race traffic at dark, so if you are behind a 30-hour pace after dark, volunteers will pull you from the course, though you still earn a 50-mile finisher buckle if you reached that point.

How should I fuel for Tunnel Hill 100?

A flat course still means a long time on your feet at 100 miles. Aim for roughly 60 to 90 grams of carbohydrate per hour, and use the aid stations along the crushed-limestone trail for regular resupply. Mid-November in southern Illinois can run cool, especially overnight for 100-mile runners still out on course, so plan layers alongside your fueling.

Is Tunnel Hill 100 a good course for a fast 100 or a Western States qualifier?

Yes. The flat, non-technical crushed-limestone surface removes the elevation-change variable that slows finish times at mountain 100s, which is part of why five world records have been set here. As the 2026 USATF 50-Mile National Championship, it also draws a competitive field at the 50-mile distance, and both the 100-mile and 50-mile races carry Western States qualifying status.

What happens if I do not finish the 100 mile at Tunnel Hill?

If you complete the first 50-mile loop but cannot continue to 100 miles within the time limits, you are not left empty-handed: your 50-mile split is recorded as your finish, and you receive a 50-mile finisher's buckle if you want it. That is a meaningful safety net on a course where the second 50 has to start within 15 hours of your first step.

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This guide is independent and for planning only. The course details, dates, cutoffs, and registration windows come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.

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