User:Gauß/Turn Restrictions

From OpenStreetMap Wiki
Jump to: navigation, search

Problems with the current turn restriction relation

1. It isn't possible to visualize all traffic signs that are in use. Only a small subset is available, so that other traffic signs are replaced with equivalents. Some of those equivalents are unusual in certain countries. Example: No straight on b.png instead of Only left turn or right turn.png.
2. It isn't possible to fix the above problem by replacing some of those currently allowed traffic signs with local variants, because the meaning isn't exactly the same. For example: only_straight_on_or_right_turn (which doesn't exist) is usually expressed as no_left_turn which is equivalent at conventional crossings but not at T-crossings:
Sign alternative 1.png Sign alternative 2.png Sign alternative 3.png
3. It isn't possible to express country specific styles of traffic signs, like for example different arrow forms or different color sets. (Brazil, Sweden, etc.)
Examples:
Only left turn b.png instead of Only left turn a.png
Only right turn c.png instead of Only right turn a.png
No u turn b.png instead of No u turn a.png
No left turn se.png instead of No left turn b.png
4. It isn't always possible to express turn restrictions in a single relation. In many cases several turn restriction relations are combined. All traffic signs of those relations are supposed to be rendered.
5. Another missing class of turn restrictions: Only half left turn.png Only half right turn.png Only half left back turn.png Only half right back turn.png No half left turn.png No half right turn.png No half left back turn.png No half right back turn.png

Some traffic signs

Traffic sign Turn restriction Remark
1 Only straight on or right turn.png only_straight_on_or_right_turn Germany, Italy, Japan, The Netherlands, Russia
2 a No left turn b.png no_left_turn Australia, Brazil, France, Ireland, Poland, Russia, Spain, Switzerland, UK, US (R3-2; R3-18 combined with no U-turn)
2 b No left turn se.png no_left_turn Sweden
3 Only straight on or left turn.png only_straight_on_or_left_turn Germany, Italy, Japan, The Netherlands, Russia
4 No right turn b.png no_right_turn Australia, Brazil, France, Ireland, Spain, Poland, Russia, Switzerland, UK, US (R3-1)
5 a Only left turn or right turn.png only_left_turn_or_right_turn Germany, Japan, The Netherlands (RVV 1990, sign D7), Poland, Russia, Switzerland, Israel
5 b No straight on b.png no_straight_on Brazil, Ireland, US (UK and France never use such signs - you would usually see adjacent left-turn-only and right-turn-only signs in such a situation; see 5 a)
6 a No u turn a.png no_u_turn Germany, France, Japan, Spain, Poland, Switzerland, Brazil, The Netherlands, US (R3-4), Israel, Russia
6 b No u turn b.png no_u_turn Australia, United Kingdom
7 Only u turn.png only_u_turn Austria
8 a Only right turn a.png only_right_turn typically on the approach to a junction
In the US, a white rectangular sign is used for this situation and for the case where one lane on a multi-lane road must turn (R3-5R)
8 b Only right turn b.png only_right_turn typically at the junction
In the US, a white rectangular sign is used for this situation and for the case where one lane on a multi-lane road must turn (R3-5R)
8 c Only right turn c.png only_right_turn Brazil
9 a Only left turn a.png only_left_turn typically on the approach to a junction
In the US, a white rectangular sign is used for this situation and for the case where one lane on a multi-lane road must turn (R3-5L)
9 b Only left turn b.png only_left_turn typically at the junction
In the US, a white rectangular sign is used for this situation and for the case where one lane on a multi-lane road must turn (R3-5L)
10 Only straight on a.png only_straight_on Used in Russia and in the United Kingdom; usually seen just before a junction or on the approach to a junction
In the US you'll see the text "NO TURNS" in a white square (R3-3; R3-5a is usually used only in the case where one lane on a multi-lane road must turn)
11 3.1 Russian road sign.svg no_entry Used for not one-way roads, where entering across some point (member node with role via) is prohibited. Relation can have several from members and one to member.
12 3.1 Russian road sign.svg no_exit Used for not one-way roads, where exiting across some point (member node with role via) is prohibited. Relation can have one from member and several to members.

Img

No left restriction.png