Written by the Nuvirox Research Team
Short answer: yes, and it's not really about the physical effort. A two-hour highway drive can leave you more drained than a two-hour walk, because driving — especially on familiar, monotonous roads — is what researchers call a vigilance task, and sustaining vigilance is cognitively expensive in a way that has nothing to do with muscle fatigue.
Key Points
- Monotonous driving reliably produces measurable "vigilance decrement" — a documented decline in sustained attention over time on task.
- The fatigue is a passive, underload state, not overload: too little stimulation is paradoxically as tiring as too much.
- Speed variability and reaction-time slowing are objective markers researchers use to detect this fatigue before drivers report feeling tired.
Why does a monotonous drive feel more tiring than an eventful one?
Because your brain is working to maintain attention against understimulation, and that work has a real cost. The theory researchers use to explain this is called attentional resource shrinkage: when a task offers little varying stimulation, arousal drifts to a low level, and vigilance — a driver's ability to detect and respond to relevant signals — degrades measurably over time, even though the driving task itself hasn't gotten physically harder.
How quickly does driving fatigue actually set in?
Faster than most people assume. A 2018 study using a 60-minute simulated monotonous drive found that cognitive fatigue and hypo-vigilance developed measurably within that single hour, tracked through both psychological ratings and physiological measures, and correlated with reduced variability in vehicle speed — drivers' speed control literally became less precise as fatigue built. Other work on real highway driving found that speed variability increased notably once a monotonous drive passed roughly 80 minutes, a rough but useful marker for when vigilance decrement tends to become behaviorally visible.
What human studies actually show
Zhang, Yan and colleagues (2018), published in Frontiers in Psychology / cited via PubMed. Twenty-one participants completed a 60-minute simulated monotonous drive while cognitive fatigue was tracked with psychological and physiological measures. Speed variability was negatively correlated with sleepiness and hypo-vigilance during the task, and drivers in the low-variability group reported more sleepiness and fatigue and less vigilance — direct evidence that the monotony itself, not distance or physical exertion, drove the fatigue.
Aitken, Downey and colleagues (2024), Journal of Psychopharmacology. This methodological review of the on-the-road driving test — a standardized real-world protocol using Standard Deviation of Lateral Position (SDLP, the car's weaving) — confirms that time-on-task is essential for detecting vigilance decrement: shorter drives systematically underestimate fatigue effects that only become measurable after sustained time behind the wheel.
The honest counterweight: most of this research uses driving simulators or standardized closed-course protocols, which don't fully capture how traffic density, conversation, music, or passenger interaction change real-world attention demands. A drive with more variability — city traffic, unfamiliar roads, a conversation partner — may produce less of this specific vigilance-decrement fatigue even though it's more effortful in other ways, so "long drive equals automatic fatigue" oversimplifies a more nuanced picture.
What this fatigue won't tell you
Feeling wiped out after driving doesn't mean anything is wrong with your reflexes or overall fitness — it's a normal, well-documented response to a specific kind of task. It's also not a reliable early-warning system: several studies note that people frequently misjudge their own vigilance state during prolonged monotonous driving, underestimating how impaired their attention has become. See a doctor if drowsiness during ordinary, non-monotonous daily activities is also a persistent problem — that pattern is more suggestive of a sleep disorder than routine driving fatigue. It is also worth noting that fatigue from monotonous driving compounds with, rather than replaces, ordinary sleep debt, so a driver who is already short on sleep will typically show the vigilance decrement described above sooner and more severely than a well-rested one covering the identical route.
What actually helps on long drives
Breaking monotony deliberately — a 15-minute stop every 90–120 minutes, varying music or podcasts, or driving with a conversation partner — addresses the underlying mechanism rather than just the symptom. Some research on speed variability suggests drivers who naturally vary their speed within safe limits maintain more vigilance than those who lock into perfectly steady cruise control, though this isn't a recommendation to drive erratically — it's a note on why cruise control on empty highways can paradoxically speed up fatigue onset. The same low-stimulation, high-vigilance-cost pattern shows up in a very different setting in why video calls are so cognitively draining, and caffeine's limits as a fix are covered in more depth in why coffee doesn't work like it used to.
What people report anecdotally
Long-haul commuters and delivery drivers who discuss driving fatigue informally often describe a specific point, commonly somewhere between 60 and 90 minutes into a monotonous stretch, where sustained attention noticeably starts to slip — a pattern broadly consistent with the vigilance-decrement timing described in the simulator research above, even though these are self-reports rather than controlled measurements.
Frequently Asked Questions
Is this the same thing as drowsy driving that causes accidents?
It's related but not identical. Vigilance decrement is the underlying attention decline; drowsy driving describes the more severe endpoint where a driver is at risk of microsleeps. The vigilance research helps explain why the latter develops.
Does caffeine fix driving fatigue?
Caffeine can temporarily improve alertness and reaction time, but it doesn't restore genuine vigilance the way a break does, and effects diminish with regular use. It's a short-term tool, not a substitute for stopping.
Why do I feel fine during city driving but exhausted after highway driving?
City driving typically provides more varying stimulation — turns, signals, pedestrians — which keeps arousal higher, while highway driving is the more classically monotonous, vigilance-decrement-prone condition.
Does passenger conversation help or hurt?
The evidence is mixed and task-dependent, but light conversation that doesn't demand deep cognitive engagement can help maintain arousal on monotonous stretches, similar to how varying music or podcasts is thought to help.
From Nuvirox
Why We Formulated NAD+ Restore
NAD+ Restore was built around the same NAD+ precursor science discussed above — formulated to support the cellular energy pathways that naturally decline with age. We're currently refining the formula further based on emerging research, so we won't list specific ingredient amounts here; the current label details are always up to date on the product page. Every order is backed by our 60-day money-back guarantee — long enough to actually evaluate it the way the research says you should.
Learn more about NAD+ Restore →The bottom line: long-drive fatigue is a genuine, well-studied phenomenon rooted in how monotonous, low-stimulation tasks tax sustained attention rather than muscles. The vigilance-decrement research is consistent and methodologically solid, though most of it comes from simulators rather than fully naturalistic driving, so real-world variability (traffic, company, road type) likely shifts individual experience more than lab studies alone can capture. Breaking up monotony with real stops remains the most directly evidence-supported countermeasure, and treating that fatigue as a genuine cognitive cost, worth planning around on long trips, is more useful than dismissing it as simply sitting still for a few hours.
References
- Zhang X, Yan X, Yang J, et al. The Relationship Between Drivers' Cognitive Fatigue and Speed Variability During Monotonous Daytime Driving. PubMed, PMID 29670563. 2018.
- Aitken B, Downey LA, Rose S, Arkell TR, Shiferaw B, Hayley AC. Vigilance decrement during the on-the-road driving tests: the importance of time-on-task in psychopharmacological research. J Psychopharmacol. 2024;38(11):998–1006.
- Larue GS, Rakotonirainy A, Pettitt AN. Driving performance impairments due to hypovigilance on monotonous roads. Accid Anal Prev. 2011;43(6):2037–2046.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice.