Kaart: Turn Restrictions/sandbox

Introduction

A turn restriction is a relation on a highway intersection that specifies turns that vehicles are either prohibited or permitted to make. These are often indicated by street signs that are explicitly marked as either a prohibitory or mandatory restriction, but some may be implied.

Roles of a Turn Restriction

There are three roles of a turn restriction:

From	The starting point for the restriction. Note: A no_entry restriction can have more than one from member.
Via	The member that connects the starting and end points together. Note: Can be a node or one or more ways.
To	The end of the restriction Note: A no_exit restriction can have more than one to member.

Street Signs

It is important to know what the different turn restrictions signs look like and how to apply them. The two tables below are small samples of real world prohibitory and mandatory traffic signs that countries use to help direct the flow of traffic.

Prohibitory Turn Restrictions
Mandatory Turn Restrictions

Prohibitory Restrictions

Turning left from a to b is not allowed at N.

This restriction prohibits you from turning in the given direction leaving all other ways accessible.

This restriction uses the following tags:

• type=restriction
• restriction=*
• Roles
  • From a
  • Via N
  • To b

Users coming from way a via way b cannot exit through way c.

The via member of the relation isn't always a node. It can also be a way(s).

The tags for this relation are as follows:

• type=restriction
• restriction=no_right_turn
• Roles
  • From a
  • Via b
  • To c

Mandatory Restrictions

Only turning right from a to b is allowed at N. So turning left is forbidden.

This restriction only allows you to turn in the give direction.

This restriction uses the following tags:

• type=restriction
• restriction=only_right_turn
• Roles
  • From a
  • Via N
  • To b

Prerequisites

Basic knowledge of relations, tagging and geometry.

Skill Instruction

JOSM has two built in tools that make turn restrictions easy.

• The turn restriction preset
• The turn restriction plugin

ID Editor also has it's own built in tool to make adding turn restrictions easy.

JOSM

Turn Restriction Preset

This tool will allow you to quickly add turn restrictions to OSM in JOSM.

To use the turn restriction preset:

• Open the Presets dropdown menu
• Hover over Relations
• Select Turn Restriction
  • Select the blue pin in the top right corner of the preset to pin it to the toolbar in JOSM.(Recommended)
  • This will open the preset window for turn restrictions.

• Click the dropdown and select the restriction type.
• Select any vehicle types that are exempt under Except.(Shift + select to select multiple types.)
• Click New relation to create the relation.
  • This will open the relation window with the newly created turn restriction.
• Apply the roles of from, via and to to their respective members.
  • Tip: If you select the members of your restriction in order of from, via and to, then the you can apply that same order from top to bottom in the relation window.

• Click Ok to apply your restriction.

Note: To see the members of the relation based on their role see the Kaart Paint Style page. The restriction signs are enabled by the JOSM default (MapCSS) paint style.

Turn Restriction Plugin

The turn restriction plugin is a slightly faster way to add turn restrictions as it does a lot of the work for you.

To add a turn restriction with the plugin:

• Select the ways and nodes in the order of From, Via, and To.
  • If you select the ways/nodes in this order the plugin will be able to tell what kind of turn restriction it is and will apply the roles and tags of the relation for you.
• Click the create a new turn restriction button on the plugin.

• Add any vehicles that are allowed to make the turn(where applicable)
  • This would make it a conditional restriction. See Conditional restrictions for more info.

• Click on the Advanced tab to add/modify tags.
  • This is where you can add tags like implicit=yes if its an implied turn restriction.

• Click Ok to apply the restriction.

This plugin also shows all relations in your area and allows you to edit or delete them.

For more information on this plugin see the Turn Restriction plugin page.

ID Editor

Adding turn restrictions in ID Editor is very simple and easy to do with the built in tool for turn restrictions.

To use this tool:

• Select a node at the intersection you want the restriction.
• From the Edit Feature popup on the left, navigate to "Turn Restictions" under Fields.
  • Adjust the Distance to include ways before the intersection.
  • Adjust the Via to include Up to 1 way or Up to 2 ways. This allows you to add restrictions that use ways as the via member like no-u-turns.
• Select a way you want to add a restriction to (typically the from member).
• Click on one of the available options to apply a restriction.
  • The name/type of restriction will be shown at the top.
  • 🟢 Green means routing is allowed.
  • 🔴 Red adds a prohibitory restriction.
  • 🔵 Blue adds a mandatory restriction.
• Deselect the feature and upload.

iD in-editor turn restriction support for via nodes	iD in-editor turn restriction support for via ways

Implicit Turn Restrictions

Implicit turn restrictions are restrictions where it's assumed that you're not allowed to go in a specific direction like driving against a oneway or that a turn should be made before that point.

We add implicit restrictions where they will improve routing. There are a lot of implicit restrictions that we don't need to add as routing software already takes them into account.

To add an implicit turn restriction:

• Create the turn restriction.
• From the relation window or Advanced tab of the plugin add the tag implicit=yes.
• Click Ok to apply the restriction.

Don't Add

Here's an example of an implicit restriction we don't need to add since you will be routed onto the link to make the right turn before you get to the intersection.

Routing without implicit restrictions
Routing with implicit restrictions

Do Add

Here's an example where implicit turn restrictions helped improve routing.

Routing with implicit restrictions
Routing without implicit restrictions

Practical Application

Use ground imagery and other context to add both explicit and implicit turn restrictions.

It is recommended to split the ways at natural stopping points like the nearest intersection to avoid over splitting ways.

Suggested Bookmarks

• Relation:restriction
• Conditional restrictions