Cited by 0Evacuation and Crowd DynamicsUrban Transport and AccessibilityTraffic and Road Safety

The DOI matches its Crossref record; 34 of the 34 references it cites were found in a registry or an index; 3 of the 27 sources its claims cite were checked for support.

Machine learning estimation of off-trail pedestrian travel rates using LiDAR-derived slope, vegetation, and surface roughness

Open access
Cutler, Sierra L., Campbell, Michael J., Brewer, Simon C., Dennison, Philip E.·2026·GIScience & Remote Sensing

Abstract

Multiple landscape factors, including slope, vegetation density, and surface roughness, work together to affect pedestrian travel rates in off-path environments. Most previous pedestrian travel rate models have only quantified the effects of these factors at relatively coarse spatiotemporal resolutions, ignoring the fine-scaled information contained within LiDAR data and instantaneous travel trajectories. Previous studies have also relied on parametric function fitting to model off-path travel rates. This paper presents the first known examination of instantaneous travel rates using random forests—a machine learning algorithm well-suited to the presence of non-linear relationships and the ability to robustly evaluate variable importance. Principal components of airborne LiDAR-derived slope, vegetation density, and surface roughness were used as predictor variables in a random forest model. The model explained over 77% of the variance in observed travel rates from an independent test dataset (R² = 0.778). An analysis of permutation importance indicated that LiDAR-derived slope was the most important predictor of travel rate, followed by vegetation density, then surface roughness. Examining the importance of slope, vegetation density, and surface roughness together provides new insight beyond their individual effects, revealing how these landscape factors interact to shape pedestrian travel rates. While slope is the most important single predictor, our results show that vegetation density and surface roughness exert distinct and nonlinear influences that become clearer only when evaluated jointly. Notably, vegetation density reduces travel rate more sharply than surface roughness, and high vegetation density remains strongly limiting even when roughness is low, whereas the reverse is not true. These combined effects also exceed the explanatory power of individual median speed, underscoring the importance of environmental conditions over individual-level differences in exertion or fitness. Potential applications of this work include modeling instantaneous travel rates for wildland firefighter safety, search and rescue, and migration applications.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This paper models instantaneous off-trail pedestrian travel rates using a random forest with LiDAR-derived slope, vegetation density, and surface roughness, plus individual median travel rate. The model explained 77.8% of variance in independent test data, with slope the most important predictor, followed by vegetation density, surface roughness, and median travel rate.

Key findings

  • The random forest explained over 77% of variance in observed instantaneous travel rates on independent test data (R² = 0.778), with RMSE = 0.160 m/s, MAE = 0.119 m/s, nRMSE = 0.350, and nMAE = 0.261.
  • Permutation importance ranked LiDAR-derived slope PC1 as the most important predictor, followed by vegetation density, then surface roughness, then individual median travel rate.
  • Partial dependence showed slope–travel rate patterns resembling asymmetrical Lorentz functions, vegetation density reducing travel rate nonlinearly with rapid initial decreases, and surface roughness reducing travel rate more linearly.
  • Bivariate partial dependence indicated vegetation density reduces travel rate more sharply than surface roughness; high vegetation density strongly limits travel rate even when roughness is low, whereas high roughness does not do the same when vegetation density is low. A model excluding median travel rate still explained over 65% of variance.

Methods

  • Nine volunteers walked eleven 100 m transects in the Central Wasatch Mountains, Utah, in both upslope and downslope directions, yielding 74 tracks; airborne LiDAR from USGS 3DEP (2018–2020, 12–16 pulses/m²) was used to derive landscape metrics.
  • Instantaneous travel rates were sampled every five seconds, producing 42,007 data points (29,405 training, 12,602 testing); predictors were PC1s for slope, vegetation density, and surface roughness, plus each individual’s median travel rate.
  • A random forest was tuned via grid search and evaluated with R², RMSE, and MAE; permutation importance and partial dependence were used to assess predictors, and XGBoost and LightGBM were fit for comparison.

Limitations

  • Stated: only nine participants were included, with substantial variation in travel rates; the authors call for a larger, more diverse sample. The five-second sampling meant slower participants generated more data points, though balancing reduced performance only slightly (R² from 0.778 to 0.763; nRMSE from 0.350 to 0.362).
  • Stated: participants travelled only about 200 m per transect, so estimated rates may be higher than over longer distances where fatigue matters; weather effects were not tested, and experiments occurred in favourable conditions.
  • Evident: the study is limited to one mountain region and a small volunteer pool, which constrains broad transferability; ALS data were collected three to five years before field experiments, though the authors checked for no substantial land cover change.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1080/15481603.2026.2626632

Cites

34 of 34 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

3 of 27 cited sources checked · 2 supported · 0 flagged · accuracy not yet measured

Show all 46 claims

  • Probably not a substantial claim. 29
  • It may state two separate claims as one. 34
56 of 56
  • The paper relies on this without support.

    The nine volunteer participants from the University of Utah are representative of off-path pedestrians in general.

    “Nine individuals of various ages, genders, and athletic abilities walked eleven transects wearing an Emesent Hovermap mobile laser scanner (MLS) mounted on a backpack.Participants were recruited volunteers from the University of Utah.”
  • The paper relies on this without support.

    The eleven transects are representative of the wider range of off-path landscapes to which the findings are claimed to apply.

    “The wide range of vegetation densities, vegetation types, and degrees of slope were chosen to make the findings of the study applicable to a wider range of landscapes than past efforts that have been focused on more ecologically narrow settings.”
  • The paper relies on this without support.

    The median travel rate across all experimental transects adequately captures individual-level differences in exertion or fitness.

    “Instead, to build a more broadly applicable model, we opted to include the individuals' median travel rates across all experimental transects as a predictor variable.”
  • The paper relies on this without support.

    In most landscapes, slope, vegetation density, and surface roughness interact to determine travel rate rather than acting in isolation.

    “In most landscapes, these variables interact to determine travel rate rather than acting in isolation.”
4 of 4

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Vegetation height ranges do not yield 37 variables

    Minor

    The specified minimum and maximum heights, at 0.25 m intervals and with a range of at least 0.5 m, permit 5 + 4 + 3 + 2 + 1 = 15 height ranges. Applying each range to all three wedge segments would yield 45 variables, not 37.

    Reported 37 · recomputed 15

  • Figure 1 caption gives two transect counts

    Minor

    The same caption says Figure 1 shows nine transects and then says it contains a map for each of eleven transects.

2 of 2

Citations

Cites

Flagged first, then by citations

Show all 33 references

Research works printed but not linked: 5

  1. Alexander, M. E., G. J. Baxter, and G. R. Dakin. 2005. “Travel Rates of Alberta Wildland Firefighters Using Escape Routes.” In Proceedings of the Eighth International Wildland Fire Safety Summit B.W. Butler and M. E. Alexander, eds. 1–12. International Association of Wildland Fire.
  2. Jensen, D. E. 2003. “Geoglyphs and GIS: Modeling Transhumance in Northern Chile.” In The digital heritage of archaeology,M. Doerr and S. Apostolis, eds. 6. Heraklion.
  3. Ke, G., Q. Meng, T. Finley, T. Wang, W. Chen, W. Ma, Q. Ye, and T.-Y. Liu. 2017. “LightGBM: A Highly Efficient Gradient Boosting Decision Tree.” In Advances in Neural Information Processing Systems 30: 1–9.
  4. Mink, P. B., M. J. Ripy, K. Bailey, H. B. Box, and T. Grossardt. 2009. Predictive Archaeological Modeling Using GIS-based Fuzzy Set Estimation In Transportation Research Board Annual Meeting11–15, Washington: ESRI International.
  5. Rogers, S. R., C. Collet, and R. Lugon. 2014. “Least Cost Path Analysis for Predicting Glacial Archaeological Site Potential in Central Europe.” In Across Space and Time: Papers from the 41st Conference on Computer Applications and Quantitative Methods in Archaeology Perth, 25–28 March 2013,Traviglia, A., ed. 261–275. Amsterdam University Press.

Cited by

Still being checked.

Metadata

Authors
Cutler, S. L., Campbell, M. J., Brewer, S. C., & Dennison, P. E.
Affiliations
  • University of Utah (US)
  • School of Environment, Society & Sustainability, University of Utah
Corresponding author
Cutler, Sierra L.
Venue
GIScience & Remote Sensing
Published
2026-02-09
Volume
63
Issue
1
ISSN
  • 1548-1603 (ISSN-L)
  • 1943-7226
OpenAlex
W7128507901
Cited by
0
References
33
FWCI
0.00
Type
journal article
Language
en
Open access
Locations
  • GIScience & Remote Sensing (publishedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • US forest service (21-CS-11221636-120)
  • National Science Foundation United States (2117865)
Topics
  • Social Sciences › Safety Research › Evacuation and Crowd Dynamics
  • Social Sciences › Transportation › Urban Transport and Accessibility
  • Physical Sciences › Engineering › Safety, Risk, Reliability and Quality › Traffic and Road Safety
Keywords
airborne laser scanning, slope, vegetation density, surface roughness, random forest, permutation importance, landscape factors, search and rescue, wildlife migration

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