Roads on a USGS topo map are graded by how big and how good they are. Red fill means a highway. Solid black double lines are roads a passenger car can drive all year. Dashed double lines are rough roads, and a single dashed line is a trail. Railroads are black lines with cross-ties.
What does a dashed black line mean on a topo map?
A single dashed black line is a trail. Two parallel dashed lines are an unimproved or 4WD road, which may need high clearance. Solid double lines are light duty roads, and red-filled lines are highways.
IN THIS GUIDE
Highways and everyday roads · Backcountry roads and trails · Bridges, overpasses, and tunnels · Railroads · Choosing a route · FAQ
Highways and everyday roads
On provisional-edition maps, all of these roads are simply classed as improved roads and drawn like light duty roads.
Primary highway
A solid red line with dark edges. The main routes, usually numbered U.S. or state highways.
Secondary highway
Red dashes inside black edge lines. Smaller state and county highways.
Light duty road
Two thin parallel lines with no fill, or a single gray line on some editions. Paved or gravel roads that a passenger car can drive all year.
Light duty road, paved USGS–Forest Service quads
USGS–Forest Service quads split light duty roads by surface. This version is paved.
Light duty road, gravel USGS–Forest Service quads
Light duty road with long gray dashes inside: a gravel surface.
Light duty road, dirt USGS–Forest Service quads
Light duty road with short gray blocks inside: a dirt surface. Can turn to mud in wet weather.
Light duty road, unspecified USGS–Forest Service quads
Light duty road with no surface information.
Highway or road with median strip
Two road symbols side by side: a divided highway.
Highway or road under construction
A dashed road symbol, often labeled Under Const. It may be finished now, or it may never have been built.
Backcountry roads and trails
These are the symbols to check before you head out on a dirt road or plan a hike.
Unimproved road
Two parallel dashed lines, or a fine gray line on some editions. A rough, usually dirt road that may need high clearance and can be impassable when wet.
Unimproved road (Forest Service style) USGS–Forest Service quads
The same road class in the style used on USGS–Forest Service quads.
4WD road
Long dashed double lines. Plan on needing four-wheel drive and good clearance.
4WD road (Forest Service style) USGS–Forest Service quads
The 4WD road in the style used on USGS–Forest Service quads.
Trail
A single dashed black line. A foot, horse, or pack trail. Trails change faster than roads, so check the map date and recent trail reports.
Trailhead USGS–Forest Service quads
A red TH in a box marks a trailhead with parking or an access point.
Gate on road USGS–Forest Service quads
A short red bar with a dot at each end, across the road. Gates may be locked seasonally or permanently.
Road block, berm, or barrier USGS–Forest Service quads
A heavy black bar across the road. The road is closed to vehicles beyond this point, often by an earth berm or boulders.
Bridges, overpasses, and tunnels
Where roads cross water or each other, the symbol tells you which one goes on top.
Highway or road underpass; overpass
The road on top is drawn unbroken. The road passing underneath is interrupted where it goes below.
Highway or road bridge; drawbridge
Short angled ticks at each end where the road crosses water. A small circle in the middle marks a drawbridge.
Highway or road tunnel
The road switches to dashed lines between angled portal marks at each end of the tunnel.
Railroads
Railroads are black lines with short cross-ties. Older maps show many lines that have since been abandoned, and plenty of those grades are now rail trails.
Standard gauge railroad, single track
A single black line with evenly spaced cross-ties. Standard gauge (4 ft 8½ in between the rails) is used on nearly all U.S. railroads.
Standard gauge railroad, multiple track
Two lines with paired ties: two or more tracks side by side.
Narrow gauge railroad, single track
A line with short, offset ties. Narrow gauge track was common on mountain and mining railroads and survives mostly as scenic lines.
Narrow gauge railroad, multiple track
Multiple narrow gauge tracks.
Railroad siding
A short track branching off and rejoining the main line, used for passing trains or loading.
Railroad yard
Many parallel tracks fanning out from the main line, where trains are sorted and stored.
Railroad turntable; roundhouse
A circle (the turntable) next to a curved black building (the roundhouse) where steam locomotives were serviced. Mostly on older maps, and a good clue for history hunters.
Railroad in highway
Track running along the middle of a highway.
Railroad in road
Track running down a road, like a street-running line in town.
Railroad in light duty road USGS–Forest Service quads
Track running down a light duty road.
Railroad underpass; overpass
The railroad passing under or over a road. Whichever line is drawn unbroken is on top.
Railroad bridge; drawbridge
Angled ticks where the track crosses water. A small circle marks a drawbridge.
Railroad tunnel
The track turns to dashed lines between tunnel portals.
WATCH
Topo Map Reading, part 6: Map Symbols
Contour lines, benchmarks, rivers, streams, lakes, swamps, roads, trails, buildings, and campgrounds in under a minute.
Watch the full Topo Map Reading series →Choosing a route
- Check the map date. Roads and trails are shown as they were when the map was made. New roads, closures, and relocated trails won't appear on an older edition.
- A line on the map isn't permission. Roads and trails can cross private land. Look at the boundary lines, and look for gates.
- Read the contours along the route. Count how many contour lines a trail crosses to estimate the climb. Switchbacks show up as a zigzag across tightly packed contours.
- Old railroad grades make great routes. They hold a gentle, steady grade. Historic maps show lines that have since been pulled up.
PUT IT TO USE
See these symbols on a real map
Frequently asked questions
What's the difference between an unimproved road and a 4WD road on a topo map?
Both are dashed double lines. Unimproved roads are rough, usually dirt roads that may need high clearance. 4WD roads use longer dashes and generally need four-wheel drive.
How are hiking trails shown on a topo map?
Trails are a single dashed black line. Some maps label the trail name or number alongside it.
What do red roads mean on a topo map?
Red fill marks highways. A solid red line is a primary highway, and red dashes inside black lines are a secondary highway.
Are all trails shown on USGS topo maps?
No. Each map shows the trails known when it was made, so newer trails may be missing and some old ones may be gone. Check the date in the map margin.
MORE SYMBOL GUIDES
Building, Campground & Landmark Symbols on Topo Maps · Boundary Lines on Topo Maps: States, Counties, Parks & Public Land · Contour Lines on Topo Maps: Index, Intermediate & Depression Contours
← Back to all USGS map symbols
Symbol artwork from the U.S. Geological Survey Topographic Map Symbols brochure (public domain).