OpenStreetMap now has comprehensive data on sealed and unsealed roads across New South Wales, Australia

A small milestone for OpenStreetMap editors and users in Australia: OpenStreetMap now has comprehensive data on sealed and unsealed road surfaces for virtually all roads in New South Wales (NSW).

Many 4WD, overlanding, cycling and routing apps get their data on sealed and unsealed roads from OpenStreetMap, so this milestone has obvious practical utility. The achievement was made possible by the amazing work of thousands of mappers.

This post celebrates and explores OpenStreetMap’s fantastic data on sealed and unsealed roads in New South Wales, Australia. I hope you enjoy it.

Map 1. Virtually all roads in regional New South Wales now have surface data. This map shows part of northern New South Wales. Blue = sealed and orange = unsealed roads. You can click on any of the maps for a larger view.

What road classes are included?

OpenStreetMap has comprehensive data on sealed and unsealed road surfaces across the entire ‘general-purpose road network’ in NSW. This includes virtually all road ways in the following highway classes: highway=motorway, trunk, primary, secondary, tertiary, unclassified, residential and all types of link roads (highway=trunk_link, primary_link, etc). The following discussion is based on these highway classes only. Surface data is incomplete for other highway classes, such as bush tracks and minor service roads (e.g. back alleys and driveways).

Throughout this post I use the term ‘surface data’ to refer to road ways that have an accepted surface tag (surface=paved, asphalt, etc.) as listed on the OpenStreetMap wiki page.

How many roads do and don’t have surface data?

As of December 2022, surface data exists for 99.8% of the total length of roads in New South Wales. Some quick stats:

• Total length of NSW roads = 209,177 km.
• Length of roads with surface data = 208,693 km (99.8%)
• Length of roads with no surface data = 484 km (0.2%).

These stats can also be expressed in terms of the number of ‘ways’ (i.e. road segments) that mappers have added to OpenStreetMap, as follows:

• Total number of road ways in NSW = 275,987 ways.
• Number of road ways with a surface tag = 272,206 (98.6%)
• Number of road ways with no surface tag = 3,781 (1.4%)

The great bulk of the road ways that do not have surface tags are in greater Sydney. In reality, virtually all of those will be sealed (see below for more details).

Map 2. Sealed roads in New South Wales. Unsealed roads are not shown. The header image at the top of this post shows a close-up of the Sydney region.

What surface data exists?

Three tags — asphalt, paved and unpaved — collectively account for 96% of all road ways that have a surface tag and 93% of the total length of all ways that have a surface tag.

About 2% of road ways are tagged as being concrete. All other surface tags (such as gravel, dirt, etc.) have been used for fewer than 1% of both the total number and the total length of all ways that have a surface tag.

There’s a more detailed breakdown of surface tags at the end of this post.

Why do some roads not have surface data?

Roads without surface data fall into three main groups:

1. miscellaneous city roads in greater Sydney, including lots of link or ‘slip’ roads.
2. roads in new housing estates, mostly in greater Sydney but also in regional towns.
3. a small number of regional roads where surfaces are not clearly visible on satellite images.

City roads

Most roads in Sydney have surface tags, but there are many short road segments that lack a surface tag, as can be seen in the map below. Virtually all of these roads will be sealed on the ground. A surprising number of these are ‘link’ roads (highway=primary_link, etc).

While the total length of these roads is short when compared to the state-wide totals, there are thousands of them. It’s a manageable task to clean them all up, but it’d be pretty tedious work.

Map 3. Roads with no surface tags (red) in Sydney. For some reason, many link roads have no surface tags. Sealed roads are shown in blue.

New housing estates

The other major group of roads that do not (yet) have surface data is in new housing estates. These roads have been mapped while under construction or shortly after being constructed but the completed road (and hence the road surface) is not yet visible on available aerial images. Again, nearly all of these roads will end up being sealed.

Map 4. Roads with no surface tags (red) in new housing estates in western Sydney. Sealed roads are shown in blue.

Surfaces obscured

The third group of roads that lack a surface tag are roads where the surface has not been ground-truthed and is not clearly visible on available imagery. Most of these are obscured by trees. There are actually surprisingly few of these. Most are in forested areas in the east of the state, on or east of the Great Dividing Range. As a consequence, virtually all roads in western and central NSW now have surface tags, apart from small, new housing estates in some country towns.

Map 5. Nearly all roads in regional NSW now have surface tags. This map shows northern NSW, north of the greater Sydney region. The circles show all roads in the region that have no surface data. Red circles show roads that cannot clearly be seen on available imagery. Most blue circles are in new housing estates in regional towns. All other roads in the region have surface tags.

How accurate is the road surface data?

There hasn’t been any formal assessment of the accuracy of road surface tags in NSW. An earlier review found that OpenStreetMap’s data on road surfaces in Victoria, Australia, was extremely accurate when compared against the state government’s dataset. My impression is that NSW data is of comparable, high accuracy.

Other Australian states

This small milestone obviously builds on heaps of earlier achievements by OpenStreetMap’s editors, especially mapping all roads in the first place! Road surface data is increasing rapidly, thanks in part to the availability of higher resolution aerial and Mapillary imagery. For instance:

• Across all of Australia, all major roads except those in Melbourne and Perth had a surface tag when assessed in mid-2021. This included all roads from motorway to tertiary, but not all residential or unclassified roads.
• In Victoria, virtually all unclassified roads (except those in Melbourne) had a surface tag by December 2021.
• I’ve focused on NSW here, but OpenStreetMap also has comprehensive data on sealed and unsealed roads in the Australian Capital Territory (ACT). The gaps in the ACT dataset are much the same as in Sydney. While most roads in Canberra do have a surface tag, hundreds do not, especially link roads and roads in new housing estates.
• Thus, NSW and the ACT are the first Australian states to have comprehensive data on road surfaces across the entire ‘general-purpose road network’, including virtually all unclassified and residential roads.

It’s not hard to imagine that OpenStreetMap will have comprehensive data on sealed and unsealed roads across all of Australia in coming years. Which state will be next?

Map 6. OpenStreetMap also has excellent data on road surfaces in the Australian Capital Territory. Blue roads are sealed. Roads with no surface tag are shown in red. As in Sydney, lots of link roads do not have surface tags.

Detailed data

For those keen to see more information, here’s a more detailed summary of the New South Wales road surface data in tables and maps. All analyses were conducted using Overpass Turbo on 15 December 2022.

According to OpenStreetMap data, the total length of roads in NSW is 209, 177 km. Unclassified roads (i.e. ‘local’ non-residential roads) account for 42% of the total length of these roads (88,239 km, see Table 1 below).

Table 1. Total length of roads in each highway class in New South Wales, and the % of the length of each group that does not have a surface tag in OpenStreetMap.

Highway type	length (km)	% no surface data
motorway	3,438	0.6
trunk	5,634	0.0
primary	10,117	0.0
secondary	24,329	0.0
tertiary	42,322	0.0
residential	34,325	0.7
unclassified	88,239	0.1
link roads	772	17.2
Total	209,177	0.2

Well over 99% of the total length of roads in each highway class now has a surface tag. The notable exception is link roads (i.e. highway=primary_link, etc.) for which a whopping 17% do not have surface data (Table 1). These are all in greater Sydney and, on the ground, all of them will be sealed.

Table 2. The proportion of sealed and unsealed roads in each highway class in NSW.

Highway type	% sealed	% unsealed
motorway	100	0
trunk	100	0
link roads	100	0
primary	99	1
residential	91	9
secondary	81	19
tertiary	54	46
unclassified	17	83
Total	52	48

Just over half of the total length of roads in NSW is sealed (52%; see Table 2 above). Not surprisingly, all motorways and trunk roads are sealed. At the other extreme, 83% of the total length of unclassified roads is unsealed. Nearly all unsealed roads are in regional, non-urban areas.

Map 7. Most unsealed roads in NSW are in regional areas, and most unsealed roads are local, unclassified roads. Sealed roads are in blue and unsealed roads in orange.

Table 3. Most frequently used surface tags on NSW roads

Surface tag	number of ways	% ways
asphalt	143,615	53
paved	87,325	32
unpaved	29,850	11
concrete	5,823	2
gravel	2,406	1
dirt	1,930	1
all others	1,257	0.5
Total	272,206	100

Three surface tags — asphalt, paved and unpaved — account for the great bulk of surface tags used. Collectively these three tags have been used on 96% of road ways (Table 3 above).

A slightly different pattern emerges if you look at the total length of road ways with each surface tag instead of the number of road ways with each tag. Unpaved road ways account for just 11% of the total number of ways (see Table 3 above) but 41% of the total length of roads (Table 4). This difference is due to the fact that unpaved road ways in rural areas tend to be much longer than short, paved road ways, many of which are in cities.

Table 4: Most commonly used surface tags in NSW, by length

Surface tag	% length
unpaved	41
asphalt	40
paved	12
gravel	3
dirt	2
concrete	1
all others	0.8
Total	100

Explore the patterns

Road surface tags aren’t shown on the standard OpenStreetMap Carto map render, but you can easily view them using Overpass Turbo. All the maps in this post were created using Overpass Turbo. The three Overpass queries below let you view OpenStreetMap’s road surface data in different ways.

Sealed roads

This query shows sealed roads only (in blue). Map 2 and the header image in this post were made using this query. Click here to make this query run.

Sealed and unsealed roads

This query shows sealed and unsealed roads in prominent colors. It works well when used over relatively small areas where there are many sealed and unsealed roads. Maps 1 & 7 in this post were made using this query. Click here to make this query run.

Sealed and unsealed roads and roads with no surface tags

This query is great for finding roads without a surface tag, so that the appropriate surface tag can be added. Sealed roads are shown in blue, unsealed roads in grey and roads without a surface tag in red. Maps 3, 4 & 6 were made with a similar query. Click here to make this query run.

How to run the Overpass queries

To run any of the three queries above, do the following:

• Click on one of the links above. This will open the Overpass Turbo in a new web page.
• Push the green Run button at the top left of the screen. Wait a bit and it will create a map of your area with sealed and unsealed roads shown in prominent colors.

The first time you use Overpass Turbo, your map might be covered in gazillions of small circles. If so, you just need to change one of the settings to turn them off. You only have to do this once.

• Click on the settings button at the top of the Overpass Turbo page.
• Scroll down and tick the box that reads ”don’t display small features as POIs”.
• Push the save button at the bottom of the dialog box.
• Then push the green Run button at the top left of the page to load a new map. It should look like the maps shown in this post.
• You can move the map to anywhere you like and then push the Run button again. It’s best to keep the region small or the query may crash.

Acknowledgements

This post celebrates OpenStreetMap’s comprehensive road data. I hope you enjoyed it and learnt something new. It’s an honour to acknowledge the thousands of editors who have compiled this amazing resource.

Related posts

• Australian roads: exploring sealed and unsealed roads in OpenStreetMap
• Sealed and unsealed roads in Victoria, Australia: OpenStreetMap’s road surfaces are super accurate
• The Great Vic Gravel Route: crossing Victoria on unsealed roads.