[Talk-us] Tagging 'advance' turn restrictions

Kevin Kenny kevin.b.kenny+osm at gmail.com
Wed Apr 5 18:09:38 UTC 2017

Near where I live, there are several places where lane restrictions
continue for several city blocks. These 'advance' turn restrictions are
confusing to human drivers, and so far it seems that navigation systems
can't cope with them at all. I'm wondering if it's even possible under our
current schemes to tag them.

Here's a typical example.

Nott Terrace, approaching Eastern Avenue/Liberty Street.

The leftmost lane may go straight or turn left on Liberty Street. Traffic
going straight will be required to turn left at the next intersection
(Union Street), and proceed straight on Union Street at the following

The center lane must go straight across Eastern Avenue. Traffic in this
lane will be required to turn left on Union Street, and then will be
required to turn right on Seward Place.

The right lane may turn right on Eastern Avenue, or may proceed straight.
Traffic going straight will be required to turn right on Union Street.

The restrictions on traffic going straight are confirmed by signage at the
next intersection https://goo.gl/maps/Soy6NxDprBG2 - the left lane must go
west on Union Street, the center lane north on Seward Place, and the right
east on Union Street.

The pavement markings are in poor condition on the Google Maps images, but
recently refreshed to show solid white lines between the lanes throughout
this entire stretch. There is essentially no opportunity to change lane in
this sequence, so a driver must choose the appropriate lane when
approaching Eastern Avenue from the south, committing to a series of
actions through the next three intersections.

Not shown in Google Street View yet, but present on the ground, are equally
confusing restrictions on Nott Terrace approaching State Street in the
opposite direction. One lane must turn left on State Street, the next lane
goes straight through that intersection but turns left on Albany street,
and the third line either turns right on State or goes straight through
onto Veeder Ave.

Do we have a scheme for tagging such a beast? I've been reading
http://wiki.openstreetmap.org/wiki/Relation:restriction which appears to be
the closest thing I've found on the Wiki, but I'm having trouble putting
the pieces together to describe these situations. I'm guessing that I'm
missing something.

Please keep your comments about the traffic engineers around here to
yourself. I don't claim that these restrictions are wisely chosen. The
Powers That Be change them up every few years, without noticeable effect on
the rate of traffic accidents. Accidents involving confused drivers making
an unlawful or unsafe lane change in these stretches are common.
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