Global Friction Surface 2019

Dataset Availability
2019-01-01T00:00:00 - 2020-01-01T00:00:00
Dataset Provider
Earth Engine Snippet
accessibility friction oxford map jrc twente


This global friction surface enumerates land-based travel speed for all land pixels between 85 degrees north and 60 degrees south for a nominal year 2019. It also includes "walking-only" travel speed, using non-motorized means of transportation only. This map was produced through a collaboration between MAP (University of Oxford), Telethon Kids Institute (Perth, Australia), Google, and the University of Twente, Netherlands. This project builds on previous work published by Weiss et al 2018 (doi:10.1038/nature25181). Weiss et al (2018) utilised datasets for roads (comprising the first ever global-scale use of Open Street Map and Google roads datasets), railways, rivers, lakes, oceans, topographic conditions (slope and elevation), landcover types, and national borders. These datasets were each allocated a speed or speeds of travel in terms of time to cross each pixel of that type. The datasets were then combined to produce a "friction surface"; a map where every pixel is allocated a nominal overall speed of travel based on the types occurring within that pixel. For the current project, an updated friction surface was created to incorporate recent improvements within OSM roads data. Differences between this friction surface and the 2015 version (Weiss et al. 2018) are not necessarily indicative of changes in infrastructure (e.g., new roads being built). Such discrepancies are far more likely to be associated with improved data quality, in particular updates made to OSM road coverage. As a result, comparisons between the friction surfaces and resulting travel time maps should be done cautiously and generally not interpreted as representing changes in access over time.

This map represents the travel speed from this allocation process, expressed in units of minutes required to travel one metre. It forms the underlying dataset behind the global healthcare accessibility map described in the referenced paper.

Source dataset credits are as described in the accompanying paper.



Name Units Min Max X Pixel Size Y Pixel Size Description
friction minutes/meter 0.000429 87.3075 30 arc seconds 30 arc seconds

Land-based travel speed.

friction_walking_only minutes/meter 0.012 87.3075 30 arc seconds 30 arc seconds

Land-based travel speed using non-motorized transport.

Terms of Use

Terms of Use

This work is licensed under a Creative Commons Attribution 4.0 International License.


  • D.J. Weiss, A. Nelson, C.A. Vargas-Ruiz, K. Gligorić, S. Bavadekar, E. Gabrilovich, A. Bertozzi-Villa, J. Rozier, H.S. Gibson, T. Shekel, C. Kamath, A. Lieber, K. Schulman, Y. Shao, V. Qarkaxhija, A.K. Nandi, S.H. Keddie, S. Rumisha, E. Cameron, K.E. Battle, S. Bhatt, P.W. Gething. Global maps of travel time to healthcare facilities. Nature Medicine (2020).

Explore in Earth Engine

var dataset = ee.Image('Oxford/MAP/friction_surface_2019');
var landBasedTravelSpeed ='friction');
var visParams = {
  min: 0.0022,
  max: 0.04,
  palette: [
    '313695', '4575b4', '74add1', 'abd9e9', 'e0f3f8', 'ffffbf', 'fee090',
    'fdae61', 'f46d43', 'd73027', 'a50026'
Map.setCenter(43.55, 36.98, 4);
Map.addLayer(landBasedTravelSpeed, visParams, 'Land-based travel speed');