Exit Info

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motorway_link tagging best practice

There are two methods to assign exit sign information into OpenStreetMap:

  1. The collective node and way method - the exit sign information is stored on both nodes and ways
  2. The node only method - all of the exit sign information is stored on a node

The preferred approach is the collective node and way method for the following technical reasons:

  1. It can handle complex interchanges, as where a motorway_link and its associated reference number can split multiple times (such as 3A-B-C)
  2. It handles turnoffs different from a country's standard without requiring tagging exceptions (e.g. a 'left' exit in right side driving countries), meaning it is easier for data consumers to be programmed for it
  3. Associating the exit sign information with the *_link way clarifies route guidance
  4. Data consumers Telenav and OsmAnd(+) both issue route guidance using node-and-way, and do not support node-only tags. A tool exists for OSRM installations to convert node-only tagging to node-and-way tagging.

node-and-way method

The exit sign information is stored on both nodes and ways as follows:

Node
key value
highway motorway_junction
ref <junction/exit number> OR
noref yes (if no reference number exists)
name <Rarely used. Name of the indicated exit/interchange itself, not the exit's destination. Use destination tags for that, below.>
Way
key value
highway *_link
oneway yes
destination <toward location>
destination:ref (proposed) <branch route number>
destination:ref:to (proposed) <toward route number>
destination:street (proposed) <branch road name>
destination:street:to (proposed) <toward road name>
junction:ref <junction/exit number> Best practice is to always use this tag on the link way.*
maxspeed:advisory <safe exit speed> (Optional: populate when there is an advisory speed posted on ramp)
destination:symbol (proposed) <motorist services> (Optional: populate when there are motorist services located at exit)

* junction:ref is recommended on all outbound junction points from a motorway, and should have the same value of ref=* on the node. While a node provides user-readable indicators of an exit's reference as indicated, junction:ref gracefully handles routing edge cases unambiguously, such as:

  • 'left' exits in right-side-driving countries (and vice-versa)
  • Nodes where multiple exit references fork away from the same node

node-only method

All of the exit sign information is stored on the node where a link splits from the motorway as follows:

Node
key value
highway motorway_junction
ref <junction/exit number>
name <exit name>
exit_to <branch route number/road name> and/or <toward route number/road name> and/or <toward location>

This method was popularized in the U.S. but is no longer recommended. This method is less structured than the node-and-way method and requires routers to rewrite exit_to as destination.

Definitions

Node
Node Term Explanation
<junction/exit number> The junction/exit number from the exit sign. Examples: 236, 11A, 51A-B
<exit name> The exit name form the exit sign - this is not typical for most exits. Example from Pennsylvania Turnpike in the US: Gettysburg Pike
Way
Way Term Explanation
<toward location> The location(typically a city) that the exit/ramp/slip road will head toward
<branch route number> The route number that the exit/ramp/slip road will branch onto
<toward route number> The route number that the exit/ramp/slip road will head toward
<branch road name> The road name that the exit/ramp/slip road will branch onto
<toward road name> The road name that the exit/ramp/slip road will head toward
<junction/exit number> Populate when a exit/ramp/slip road splits at a common node and has different junction/exit numbers
Example: 51A (the node <junction/exit number> will have 51A-B)
<safe exit speed> Populate when a exit/ramp/slip road has an advisory speed sign
<motorist services> Populate when the exit/ramp/slip road has access to services motorist need

Examples

Canada

Québec

A20 Ouest km143.jpg
Node
key value
highway motorway_junction
ref 143
Way
key value
highway motorway_link
oneway yes
destination Saint-Valérien-de-Milton
destination:ref 211 Sud
junction:ref 143
maxspeed:advisory 45

United States

A/B split

Interstate 83 North ends at Interstate 81 exit sign

The above exit sign information shall be added to OpenStreetMap as follows:

Node
key value
highway motorway_junction
ref 51A;51B
Southbound Way
key value
highway motorway_link
oneway yes
destination Carlisle;Lewistown
destination:ref I 81 South;US 322 West
junction:ref 51A
Northbound Way
key value
highway motorway_link
oneway yes
destination Hazleton;Allentown
destination:ref I 81 North
destination:ref:to I 78
junction:ref 51B

Simple road name

Simple Derry Street exit sign

The above exit sign information shall be added to OpenStreetMap as follows:

Way
key value
highway motorway_link
oneway yes
destination:street Derry Street

Road name

Interstate 695 Outer Loop at Baltimore Washington Parkway exit sign

The above exit sign information shall be added to OpenStreetMap as follows:

Node
key value
highway motorway_junction
ref 7B
Northbound Way
key value
highway motorway_link
oneway yes
destination Baltimore
destination:ref MD 295 North
destination:street Baltimore-Washington Parkway
junction:ref 7B
maxspeed:advisory 25 mph

At the next exit, tag:

Next exit node
key value
highway motorway_junction
ref 6
Next northbound way
key value
highway motorway_link
oneway yes
destination Linthicum
destination:ref MD 295 North
destination:street Camp Meade Road
junction:ref 6

Exit name

Interstate 76 West at US 15 exit sign

Exit names are usually found on toll roads. On guide signs, exit names look similar to road names. The above exit sign information shall be added to OpenStreetMap as follows:

Node
key value
highway motorway_junction
ref 236
name Gettysburg Pike
Way
key value
highway motorway_link
oneway yes
destination Gettysburg;Harrisburg
destination:ref US 15
maxspeed:advisory 25 mph
destination:symbol hospital
junction:ref 236

Shared direction

040i ar exit 155 apch.jpg

This exit for northbound U.S. 67 and northbound U.S. 167 displays "North" only once, but destination:ref=* should contain "North" twice:

Node
key value
highway motorway_junction
ref 155
Way
key value
highway motorway_link
oneway yes
destination Jacksonville;Little Rock Air Force Base
destination:ref US 67 North;US 167 North
junction:ref 155

Shared exit

I-680 south at SR 4.jpg

This exit serves both eastbound and westbound State Route 4:

Node
key value
highway motorway_junction
ref 53
Way
key value
highway motorway_link
oneway yes
destination Pittsburg;Antioch;Martinez;Hercules
destination:lanes Pittsburg;Antioch|Martinez;Hercules
destination:ref CA 4
destination:ref:lanes CA 4 East|CA 4 West
junction:ref 53

A short distance later, the exit splits:

Subsequent node
key value
highway motorway_junction
noref yes
Subsequent eastbound way
key value
highway motorway_link
oneway yes
destination Pittsburg;Antioch
destination:ref CA 4 East
Subsequent westbound way
key value
highway motorway_link
oneway yes
destination Martinez;Hercules
destination:ref CA 4 West

Unnumbered exit

Ca-1 N and US 101 N just before the Ca-1 exits the US 101.JPG

This exit has no visible number signage. Unnumbered exits are common on controlled-access U.S. routes and state highways in many parts of the U.S., as well as on Interstate freeways in California.

Node
key value
highway motorway_junction
noref yes
unsigned_ref 445B
Way
key value
highway motorway_link
oneway yes
destination Mill Valley;Stinson Beach
destination:ref CA 1
junction:unsigned_ref 445B

Freeway entrance

Idaho 40 western terminus.jpg

destination=* can also be tagged on an on-ramp – a highway=motorway_link way leading to a motorway:

Way
key value
highway motorway_link
oneway yes
destination Pocatello
destination:ref I 15 North

Issues

U.S. issues

Off-ramp/on-ramp way split

When adding interchange information to ways - please review the relationship of the interchange sign information and the connected ways. Sometimes a way will need to be split between an off ramp and an on ramp. Here is an example of when interchange information was added to a way that was both an off ramp and an on ramp:

This way needs to be split because the interchange information ( destination and destination:ref) is only for the off ramp.


Thus, leading to the following invalid on ramp directions:

The 2nd maneuver has the invalid on ramp instruction.


The above way was split - here is the updated off ramp way:

Split off ramp way.


Here is the updated on ramp with the proper interchange information ( destination and destination:ref):

Fixed on ramp way.


The on ramp instruction will now be: Turn left to take the I 99 North/US 220 North ramp toward Tyrone.

The 2nd maneuver has the fixed on ramp instruction.