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Adding exit and destination signs

Mapping guides

Adding exit and destination signs

Exit number and destination mapping

Exit numbers and destinations are used as a part of guidance in routing engine. They help the driver in navigation guidance through on-ramps and off-ramps while routing on major roads.

image

What are exit numbers?

An exit number is a unique alpha-numeric identity assigned to a road junction, usually an exit from where a freeway starts. It is usually marked on the same sign as the destinations of the exit, as well as a sign in the gore. OpenStreetMap based guidance systems such as OSRM can use exit numbers as a way to guide drivers to take the right exit during navigation.

image

Different tags for mapping exit numbers:

  • highway=motorway_junction → is used in representing the specific node as a junction where the exiting way starts
  • ref=* → is used when the exit has a specific number assigned to it
    • Also tag junction:ref=* on the connecting highway=motorway_link way
  • noref=yes → is used when the exit does not have any official number assigned to it

In California, exit number signage is inconsistent. The state is gradually adding exit numbers. In the meantime, it’s common for a freeway exit to lack any exit number sign, even if Wikipedia provides an exit number. If there’s already a ref tag on the highway=motorway_junction node but no exit number sign appears in Mapillary imagery from within the past year, replace the ref tag with unsigned_ref. Sometimes there’s no exit number at the exit, but an advance guide sign (the one that says “½ mile” or “1 mile”) does display an exit number. In that case, leave the exit number in ref, because a driver would be able to use that information while navigating.

What are destinations?

Destination tags describe the content of road signposts or ground information indicating the names of the locations that a certain exit from the freeway or a highway is heading to, or that a certain entrance to the freeway is heading to. The destination tag refers to the place the entering/exiting way is leading to. Thus navigation systems can represent correct guidance with the respect to road signs that the driver actually sees when driving. The destination references are also alpha-numeric identities which changes from state to state in US. For reference check the shield dictionary to understand how highway shields are represented in different states of US. If you can’t figure out how to map a particular highway shield, look at the ref tags on the way that the motorway_link way leads to.

image

Different tags for mapping destination signs:

  • destination=* → is referring to the place/street that the ramp (link way) leads to.
  • destination:ref=* → is the route number of the roads that the ramp leads to
  • destination:ref:to=* → is the route number of the roads that the ramp indirectly leads to
  • destination:street=* → is an alternative name for the numbered route – only use in Florida, Kentucky, and Maryland
  • destination:lanes=*, destination:ref:lanes, etc. → Often the destinations of a road differ from lane to lane. To specify those for every lane, destination:lanes=* is used.

Cardinal direction:

Every dual carriage way has two oneways roads having traffic in opposite directions. Considering a dual carriage way as a destination, it is important to provide the cardinal direction of the way to which the route is navigating the user. To get this information we need to add cardinal directions to the destination:ref tags of the exit/entrance ways.

screen shot 2017-09-13 at 10 55 21 am

The cardinal direction of the road is the direction in which a road is linearly-referenced in increasing order. It is an important feature in navigation and helps in guiding the user in write direction.

How to map exit numbers and destinations?

Ground based imagery or a field survey is the only way one can verify freeway junctions and road signs. For imagery, Mapillary imagery can be used as a reference to verify and add exit numbers and destinations to mapped highways on OpenStreetMap. Sometimes the pavement is marked with a route shield in each lane, indicating the destination ref, in which case you can also use aerial imagery.

Node:

Exit numbers are mapped as nodes at the junction’s on highways where freeways have exit ways.

S.No Mapillary Image JOSM representation Tags
1 screen shot 2017-07-18 at 11 23 16 am screen shot 2017-07-18 at 11 24 50 am
  • highway=motorway_junction
  • noref=yes
2 screen shot 2017-07-18 at 11 48 11 am screen shot 2017-07-18 at 11 52 15 am
  • highway=motorway_junction
  • ref=414A
3
  • highway=motorway_junction
  • ref=51A;51B
  • ref:left=51A
  • ref:right=51B
4 screen shot 2017-07-20 at 12 28 02 pm screen shot 2017-07-20 at 12 28 49 pm
  • highway=motorway_junction
  • ref=56
Note: Some times exit numbers are placed separately
5 screen shot 2017-07-31 at 1 42 19 pm screen shot 2017-07-31 at 5 18 22 pm
  • highway=motorway_junction
  • ref=236
  • name=Gettysburg Pike

Way:

Destinations are mapped on the highway=motorway_link ways that start from the highway=motorway_junction node and connect with another road. These are called off-ramps or freeway exits. Destinations are also mapped on the highway=motorway_link ways that start from another road and end on the highway=motorway way (without a highway=motorway_junction node). These are called on-ramps or freeway entrances.

S.No Mapillary Image JOSM representation OSM tags
1 screen shot 2017-07-18 at 11 48 11 am screen shot 2017-07-18 at 11 49 17 am
  • destination=Hillsdale Boulevard
  • junction:ref=414A
2 screen shot 2017-07-18 at 12 25 22 pm screen shot 2017-07-18 at 12 27 49 pm
  • destination=Woodward Avenue;Main Street;Detroit Zoo
  • destination:ref=M 1
  • junction:ref=16
Note: M represents that highway belongs to the state trunkline highways of Michigan state
3 screen shot 2017-07-18 at 1 02 35 pm screen shot 2017-07-18 at 1 04 13 pm
  • destination:ref=I 71 North;US 50 East
  • destination:ref:to=I 471;US 52 East
  • junction:ref=1B
Note: I represents Interstate highways and US represent U.S. Routes. North and East represent the cardinal direction of the way. Only enter the cardinal direction that is used on the sign; do not guess based on the physical direction of the road.
4 screen shot 2017-07-18 at 2 16 52 pm screen shot 2017-07-18 at 2 18 59 pm
  • destination:ref=KY 1072
  • destination:street=Kyles Lane
  • destination=Fort Wright;Park Hills
  • junction:ref=189
Note: KY comes from the state of Kentucky, where oval shields represents state routes. The small letter font represents destination:street and are only available in limited US states
5 dearborn2 iD
  • destination=Dearborn Street;James Street;Madison Street;Spokane
  • destination:lanes=Dearborn Street;James Street;Madison Street|Spokane
  • destination:ref=I 90 East
  • destination:ref:lanes=|I 90 East
  • junction:ref=164A
6
  • destination=Pocatello
  • destination:ref=I 15 North
Note: Make sure to split the highway=motorway_link way at the intersection, so that the on-ramp and off-ramp are represented by separate ways.
7
  • destination:ref=I 275 West
  • destination:ref:to=I 74
  • destination=Indianapolis

Note:

  • Cardinal direction can be found on the sigh boards but this is not the same in all cases. In case, the cardinal direction is missing on the sign board do look into the route relation of the connecting motorway of the exit/entrance way and get the cardinal direction.
  • If you come across missing street level imagery, get the destination and destination:ref information from the connecting motorway of the exit/entrance way along with the cardinal direction of the way.

References:

Short forms of common words on sign boards:

Short-form Full-form
Rd Road
St Street
Dr Drive
Br Bridge
Ave Avenue
Blvd Boulevard
Pt Point
Pkwy Parkway
Cr Creek
Mtn Mountain
Mt Mount
Jct Junction
Ft Fort
AFB Air Force Base
JR Junior
MLK Martin Luther King
Co County