On Stage 1 of the 2025 Vaolta ao Algarve last week, over half the peleton went off course just before the finish and appeared on the wrong side of the finish line barriers. The ‘winner’ of the stage, Filippo Ganna of Ineos had to hang around for a long time, before being told the stage had been cancelled.

Just a couple of days before that at an amateur running race in Glasgow, over 30 runners went off course after a Prankster not only moved arrows but also impersonated a marshal with a hi-vis tabard, and sent runners on a 2.5K detour. We’ve also been victims of people moving arrows at our events and course marking disasters are far from new!

Here’s a list of 10 real-life course marking disasters that have caused chaos at running events in the past including some major races.

1. 2013 Venice Marathon – Lead Motorcycle Goes the Wrong Way (Italy)

🏃 Disaster: The lead motorcycle took a wrong turn, leading the front pack of elite runners off course by several kilometers.
🔍 Impact: An unknown runner, Eyob Faniel, who had not been in the lead, unexpectedly won the race.

2. 2018 Cardiff Half Marathon – Extra 460 Meters Added (Wales, UK)

📏 Disaster: Organizers misplaced a turnaround point, making the course 460 meters too long.
🔍 Impact: Runners were denied personal bests and qualifying times, and officials had to apologize.

3. 2015 Bristol Half Marathon – Short Course Error (UK)

📏 Disaster: The lead car directed runners onto a shortcut, making the race almost 500 meters too short.
🔍 Impact: All race records were invalidated, and runners were furious after discovering their times were not official.

4. 2014 Brighton Marathon – Confusing Course Markings (UK)

🚩 Disaster: Poor signage confused the front-runners, with some running extra distance while others skipped sections of the course.
🔍 Impact: Organizers had to adjust finishing times manually, leading to disputes.

5. 2013 Marseille-Cassis 20K – Lead Car Mistake (France)

🚗 Disaster: A police vehicle guiding elite runners went off course, causing chaos among the front pack.
🔍 Impact: Officials had to manually correct results, and some athletes lost their chance at prize money.

6. 2018 Frankfurt Marathon – Elites Misled by Marshals (Germany)

🏃 Disaster: Race marshals misdirected elite runners onto a longer section of the course.
🔍 Impact: Some athletes dropped out due to confusion, while others lost podium positions.

7. 2021 Great Scottish Run – Course Measured Wrong (UK)

📏 Disaster: Organizers discovered years later that the course had been 150 meters short due to a measuring error.
🔍 Impact: Over 20,000 runners had their finishing times invalidated for several years.

8. 2016 Northumberland Half Marathon – Runners Get Lost (UK)

🗺️ Disaster: Course signage was blown away by strong winds, leaving runners completely lost on rural roads.
🔍 Impact: Many had to guess the route, and results were disqualified due to inconsistencies.

9. 2019 Ultra-Trail Mount Fuji – Misplaced Checkpoint (Japan)

🏔️ Disaster: A checkpoint was set up in the wrong location, causing some runners to run an extra 5 km while others ran a shorter distance.
🔍 Impact: Race officials had to cancel sections of the event and issue time adjustments.

10. 2017 Birmingham Half Marathon – Course Markers Stolen (UK)

🚩 Disaster: Vandals removed course markers the night before the race, leading runners the wrong way.
🔍 Impact: Some participants ran up to 3 km extra, and race officials had to apologize and issue refunds.

These examples show how a single course marking error can ruin events large & small —whether it’s too long, too short, or completely off course.