key aspects of navigation - geometry 11. definition # 2 a street is a surfaced linear feature...
TRANSCRIPT
KEY ASPECTS OF NAVIGATION- Geometry
1
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Definition
# 2
A street is a surfaced linear feature whose normal function includes the passage of vehicles
Streets are created for or result from vehicular movement Represented in our database by chains of vector segments,
which connect at nodes Generally representation of streets is based on the centerline
of the road network When road parts converge into a complex network, real world
traffic flow is represented
- Displays the road network
- Derives route guidance
- Locates destinations
- Serves as the geometric backbone upon which all other attributes are tied
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Definition
What kinds of roads are we interested in?– Publicly accessible for through traffic
– Possesses street name
– Possesses addresses
– Potentially accessible, no name, but paved
– Inaccessible, but on captured company ground
– In a publicly accessible parking garage
– Designed for pedestrian traffic, where supported
– Pedestrian crossing over multiple carriageways that is situated at least 50 meters from the nearest intersection
– Road network intending to provide connection between other captured geometry
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Definition
What kinds of roads are there?– Single digitized (single carriageways)
– Double digitized (dual carriageways)
Where do we draw the road?– Centerline of road
– Traffic flow
How do we draw the road?– Represent reality
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Definition
Single digitized (single carriageway):– The centerline follows the center of the overall prepared roadbed,
regardless of number of lanes. Typically this is a central painted line, but it is also commonly the center of a two-way median turning lane.
Undivided road with one lane of travel going in each direction. Red line shows correct centerline representation.
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One lane on one side of a central painted line separating opposing directions of traffic flow and two lanes on the other side results in one centerline that coincides with the central painted line
Definition
Undivided road with two northbound lanes and one southbound lane. Red line shows the correct centerline representation if the road is validly represented as a single carriageway.
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Two lanes on one side of a central, two-way median turning lane and one lane on the other side results in one centerline that coincides with the center of the central lane
Definition
Undivided road with two northbound lanes, one southbound lane, and a dedicated two-way median turning lane. Red line shows the
correct centerline representation for the road.
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Definition
Double digitized (dual carriageway):– Each centerline represents the center of the traversable portion of
one side. – If median turning lanes are present for the entire length of the street
between intersections, they are considered part of the traversable portion of the street.
– Shoulders are NOT considered.
Two lanes on each side of the median results in the centerline coinciding with the central painted line on each side.
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Three lanes on one side of the divider and two lanes on the other side results in one centerline in the center of the middle lane on one side of the road, and one centerline that coincides with the central painted line on the other side of the road
Definition
divided road with three northbound lanes and two southbound lanes. Red lines show the correct center line representation if the road is validly represented as a dual carriageway
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Two lanes on one side of the divider and two through lanes plus a dedicated right-hand turn lane on the other side results in one centerline that coincides with the central painted line on one side of the road, and one centerline in the center of the middle lane on the other side of the road
Definition
divided road with two northbound lanes and three southbound lanes (one of which is a dedicated right-hand turn lane). Red lines show the correct center line representation if the road is validly represented as a dual carriageway.
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The location of a centerline passing through an intersection should only be affected by the presence of turn lanes if they exist for the entire intersection
Definition
double-digitized road where turning lanes are present only at the street intersections. Red line shows correct centerline representation.
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Definition- Single or Double Digitize?
Double digitize if there are islands, medians, or barriers:– Concrete blocks, crash barriers, waterways, railways– White shaded painted area– White line not interrupted at intersections– a combination of double/single white lines or barriers and a bus
and/or tram foundation– four yellow lines– a pair of solid yellow lines bordering an area of diagonal lines
parallel to the traffic flow– a pair of solid white lines bordering an area of white diagonal
stripes or white chevrons (both lines should be solid)– any combination of these
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Barriers can be legal or physical in nature Barriers are greater than 40 meters long (exceptions) If not, then single A turn lane or “suicide lane” is not a legal median Single digitize where opposing directions of traffic flow are
separated only by a turn lane or “suicide lane”
Definition- Single or Double Digitize?
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Definition- Single or Double Digitize?
Double-digitize around the divider since the length of the island is 40 meters (~ 130 feet)
40 m (~ 130 ft)
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Definition- Single or Double Digitize?
The same rule applies if the divider is legal
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Definition- Single or Double Digitize?
Do not double-digitize around the divider since the length of the island is 40 meters (~ 130 feet)
40 m (~ 130 ft)
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Definition- Single or Double Digitize?
Double-digitize around the entire length of the divider since the total length of the combination physical / legal divider is 40 meters (~ 130 feet)
40 m (~ 130 ft)
This is not a gap in the divider– it is a legal
median
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Definition- Single or Double Digitize?
In this example, the E-W stretch of road is single-digitized since the opposing directions of traffic flow are separated only by a turn lane
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Specifications
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Specs
Double Digitize Traffic Islands Turn Channels Pinching Intersections Offset Intersections Curved Roads Corners Dead ends/ Cul-de-Sacs
Bumps Connecting Roads SPUIs Highway Ramps Blocked Intersections Dual Carriageway Crossover
s Stacked Roads Large Intersections
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Specs - Double Digitize
Around a group of adjacent dividers if the total length 40 meters
Double-digitize around the group of adjacent islands since the total length of the divided stretch of road is 40 meters (~ 130 feet)
40 m
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Remember that the FOW for the double digitized geometry will be 3 because it did not meet length
requirements
Specs - Double Digitize
Around a divider 40 meters in length if it has a major impact on traffic flow
Double-digitize around the divider since it has a major influence on traffic flow – i.e. the island prevents
westbound traffic from turning north and southbound traffic from turning west
40 m
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Specs - Double Digitize
Around a divider 40 meters in length if it has a major impact on traffic flow cont.
Multi-digitizing around the larger divider requires multi-digitizing around the smaller divider even though the latter is 40 meters (~ 130 feet) long
40 m 40 m
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Specs - Double Digitize
If the gap between consecutive validly double digitized dividers is 40 meters.
Double-digitize around the two dividers since the length of both islands is 40 meters (~ 130 feet), and double-digitize across the gap between the dividers since the gap is 40 meters (~ 130 feet)
40 m 40 m 40 m
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Specs - Double Digitize
If the gap between consecutive dividers, one valid, is 40 meters
Continue the double-digitization around the smaller divider since it is separated from the larger (validly multi-digitized) divider by a gap 40 meters (~ 130 feet)
40 m 40 m 40 m
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Specs - Double Digitize
If the gap between consecutive dividers, at least one valid, is 40 meters cont.
Double-digitize around all three dividers since the gaps between the smaller divider and the larger (validly multi-digitized) dividers are both 40 meters (~ 130 feet)
40 m 40 m 40 m 40 m 40 m
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Specs - Double Digitize
If the gap between consecutive dividers, one valid, is 40 meters.
Do not continue the double-digitization around the smaller divider since it is separated from the larger (validly multi-digitized) divider by a gap 40 meters (~ 130 feet)
40 m 40 m 40 m
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Specs - Double Digitize
If the gap between consecutive valid dividers is > 40 meters, but has DCW appearance– Turn lane or destination access
Double-digitize around the two dividers since the length of both
islands is 40 meters (~ 130 feet), and double-digitize between the
dividers since the gap is due to a turn lane
40 m 40 m 40 m
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Specs - Double Digitize
Do not follow the > 40 meter rule if ALL apply:
– Sausages would be created (too many SCW to SCW transitions)
– Rest of road is validly single-digitized
– Median exists only at an intersection
– Non-restrictive (no streets or access roads are present on either
side of the median)
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Specs - Double Digitize
Single-digitize through the divider since: (i) the rest of the road in the area is validly single-digitized, (ii) the median exists only at the intersection, and (iii) no streets or other access roads exist (in the real world) on either side of the
temporary median – i.e. the median is “non-restrictive”
40 m
No access streets on either side of median
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Specs - Double Digitize
the roads are single-digitized at the intersection since: (i) the rest
of each road is validly single-digitized, (ii) each median exists only at the intersection, and (iii) each median is non-restrictive
40 m (~ 130 ft)
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Specs - Double Digitize
The goal of these rules is to reduce cases where strictly following the 40 meter rule described in the previous slides results in a road that resembles a link of sausages. (i.e. a road that switches back and forth between double-digitized and single-digitized over a
relatively short distance)
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Specs - Double Digitize
Bridges– Divided before and after, but not on bridge
• # lanes on bridge = # before and after• Continue across the bridge
lane dividerbarrier
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Bridges– Divided before and after, but not on bridge
• # lanes on bridge < # before and after• Don’t continue across the bridge
Specs - Double Digitize
lane dividerbarrier
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Specs - Traffic Islands
“T” Intersections– Traffic island >40 meters
Multi-digitize around the traffic island since the length of the
island is 40 meters (~ 130 feet)
40 m
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Do not multi-digitize around the traffic island since the length of the island is 40 meters (~ 130
feet) 40 m
“T” Intersections– Traffic island <40 meters
Specs - Traffic Islands
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“Y” Intersections– A “Y” intersection occurs when a triangular shaped traffic island
causes a single carriageway to split into 2 diverging non-parallel carriageways just before it intersects another road AND
– The lane separation caused by the island results in relative ambiguity between the two carriageways - i.e. it does not result in a dominant carriageway that carries the majority of the traffic and a subsidiary turn channel or slip road.
Capture if traffic island is >40 meters Measured parallel to the longest arm of the “Y”
Splitter islands associated with traffic circles (flares) should be captured only if it is>40m
Specs - Traffic Islands
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Digitize a “Y” intersection since the length of the traffic island (measured parallel to the longest arm
of the “Y”)is 40 meters (~ 130 feet)
Specs - Traffic Islands
>40m
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“Y” Intersections
– Traffic island > 40 meters
Do not digitize a “Y” intersection since the length
of the traffic island is 40 meters (~ 130 feet) 40 m
Specs - Traffic Islands
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40 meter traffic island rule does not apply to
– Traffic islands located at the end of ramp chains– Traffic islands that define turn channels
In each of these cases, the criterion for digitizing around the traffic island is 7.5 m.
Specs - Traffic Islands
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Specs - Turn Channels
Turn lanes and turn channels often exist at intersections
– Separate lane only with painted lines = Turn Lane
– Separate lane with physical or legal barrier = Turn Channel
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Specs - Turn Channels
Left Hand Turn Channel
Left Hand Turn Channel
B
D
Left Hand Turn Lane
A
Right Hand Turn Lane
Left Hand Turn Channel
C
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Specs - Turn Channels
Obstruction is > 7.5 meters External
– Right
– Left
Internal– Right
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Centerline for a road that allows vehicles to gradually depart or enter a road is drawn with an angle of 30º
Specs - Turn Channels
= 30º = 30º
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Example
Left-hand turn channel is digitized only if the “length” of the physical island, measured parallel to the slip road, is 7.5 meters (~ 25 feet)
Left-Hand Turn Channel
Must be 7.5 m (~ 25 ft) to digitize left turn
channel
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Example
The same rule applies if the slip road is separated from the main road by a legal island
Left-Hand Turn Channel
Must be 7.5 m (~ 25 ft) to digitize left
turn channel
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Example
Left-Hand Turn Channel
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Example
External left-hand turn channel is digitized only if the “length” of the physical island, measured parallel to the slip road, is 7.5 meters (~ 25 feet)
External Left-Hand Turn Channel
Must be 7.5 m (~ 25 ft) to digitize left
turn channel
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Example
The same rule applies if the slip road is separated from the main road by a legal island
Must be 7.5 m (~ 25 ft) to digitize left
turn channel
External Left-Hand Turn Channel
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Example
Internal right-hand turn channel is digitized only if the “length” of the physical island, measured parallel to the slip road, is 7.5 meters (~ 25 feet)
Internal right-Hand Turn Channel
Must be 7.5 m (~ 25 ft) to digitize
right turn channel
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Example
The same rule applies if the slip road is separated from the main road by a legal island
Internal right-Hand Turn Channel
Must be 7.5 m (~ 25 ft) to
digitize right turn channel
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Projected centerlines for opposing right hand turn channels should be represented as intersecting at a common node if they intersect the single carriageway within 5 meters
Specs - Turn Channels
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Projected centerlines for opposing right hand turn channels should be represented as intersecting a single carriageway at separate nodes if more than 5 meters apart
Specs - Turn Channels
5 m
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If opposing right hand turn channels curve away from departed roads, and projected centerlines intersect SCW > 5 meters from each other and > 5 meters from the DCW centerlines, then draw as shown.
Specs - Turn Channels
Distances x, y, and z are all > 5 meters
zyx
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If opposing right hand turn channels curve away from departed roads, and projected centerlines intersect SCW > 5 meters from each other and 5 meters from the DCW centerlines, then draw as shown
Specs - Turn Channels
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Projected centerlines for only one Right turn channel should be represented as shown
Specs - Turn Channels
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Example of correct angle for right connecting road
Turn Channels
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Example of incorrect angle for right connecting road
Turn Channels
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Specs - Turn Channels (Right Turn Lane)
Right-hand turn lanes are not multi-digitized since no obstruction, legal or physical, separates such lanes from the other lanes
No median separates right-hand turn lane
from other lanes
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Specs - “T” Intersections with Traffic Islands and Turn Channels
Do not multi-digitize around the traffic island since the length of the island is 40 meters (~ 130 feet), and do not digitize the left-hand turn channels since they are both 7.5 meters (~ 25 feet) in length
7.5 m 40 m
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Specs - “T” Intersections with Traffic Islands and Turn Channels
Multi-digitize around the traffic island since the length of the island is 40 meters (~ 130 feet), but do not digitize the left-hand turn channels since they are both 7.5 meters (~ 25 feet) in length
40 m 7.5 m
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Specs - “T” Intersections with Traffic Islands and Turn Channels
Do not multi-digitize around the traffic island since the length of the island is 40 meters (~ 130 feet), but do digitize the left-hand turn channels since they are both 7.5 meters (~ 25 feet) in length
7.5 m 40 m
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Multi-digitize around the traffic island since the length of the island is 40 meters (~ 130 feet), and also digitize the left-hand turn channels since they are both 7.5 meters (~ 25 feet) in length
7.5 m 40 m
Specs - “T” Intersections with Traffic Islands and Turn Channels
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Specs - Where to Pinch?
Double to single transition
Referred to as a pencil point
Depends on divider location
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Specs - Where to Pinch?
The angles of the Road Network Geometry representing the carriageways of the multi carriageway and the imaginary continuation of the Road Network Geometry representing the single carriageway has to be in between 30° and 40°.
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Overall taper angle goal is 60°
Specs - Where to Pinch?
60
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Specs - Where to Pinch?
Before intersection
– Divider ends ≥ 5 meters before
intersection
Begin the transition from dual carriageway to single
carriageway just before the end of the median
5 m
Correct digitization of a dual to single carriageway transition when median ends 5 meters (~ 16 feet) before the intersection
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Before intersection
– Divider ends ≥ 5 meters
before intersection
Correct digitization of a dual to single carriageway transition when median ends near the intersection but still 5 meters (~ 16 feet) from the intersection
Specs - Where to Pinch?
5 m
Locate the node along the line defined by projecting the
casings of the cross street into the intersection
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Before intersection– One-way road
Correct digitization of a dual to single carriageway transition when the single-digitized road is a one-way road
Specs - Where to Pinch?
The transition from dual carriageway to single
carriageway must occur before the intersection even if the segments cross over the
median
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Specs - Where to Pinch?
After intersection– Divider ends < 5 meters before intersection
Correct digitization of a dual to single carriageway transition when median ends 5 meters before intersection (and the single-digitized road is not a one-way road)
Begin the taper at the line defined by projecting the
casings of the cross street into the intersection
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Specs - Where to Pinch?
After intersection– Divider extends to other side
Begin the taper just before the
end of the median
Correct digitization of a dual to single carriageway transition when median ends after intersection
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Physical vs. legal divider
Correct digitization of a dual to single carriageway transition when a physical median changes to a legal median prior to terminating 5 meters (~ 16 feet) from
the intersection
Specs - Where to Pinch?
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Specs - Where to Pinch?
Left turn lanes
Correct digitization of a dual to single carriageway transition when a legal
median changes to painted lines prior to terminating 5 meters (~ 16 feet) from
the intersection
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Specs - Intersections
The following slides depict the correct digitization of intersections given the situation in reality
-4 way intersections• Double digitized • Left turn channels
-3 way intersections• Double digitized• Left turn channels
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4-way Intersection - 2 Double-Digitized
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4-way Intersection - 2 Double-Digitized
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4-way Intersection - 2 Double-Digitized
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4-way Intersection - 3 Double-Digitized
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4-way Intersection - 3 Double-Digitized
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4-way Intersection - 1 Double-Digitized with 1 Right-Hand Turn Channel
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4-way Intersection - 2 Double-Digitized with 2 Right-Hand Turn Channels
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4-way Intersection - 2 Double-Digitized with 2 Right-Hand Turn Channels
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4-way Intersection - 3 Double-Digitized with 3 Right-Hand Turn Channels
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4-way Intersection - 4 Double-Digitized with 4 Right-Hand Turn Channels
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3-way Intersection - 1 Double-Digitized
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3-way Intersection - 1 Double-Digitized
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3-way Intersection - 1 Double-Digitized
Correct digitization when median ends
5 meters (~ 16 feet) before intersection
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3-way Intersection - 1 Double-Digitized
Correct digitization when median ends 5 meters
(~ 16 feet) before intersection
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3-way Intersection - 2 Double-Digitized
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3-way Intersection - 2 Double-Digitized
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3-way Intersection - 2 Double-Digitized
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3-way Intersection - 2 Double-Digitized
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3-way Intersection - 2 Double-Digitized
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3-way Intersection - 3 Double-Digitized
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3-way Intersection - 1 Double-Digitized with 1 Right-Hand Turn Channel
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3-way Intersection - 2 Double-Digitized with 2 Right-Hand Turn Channels
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Specs - Offset Intersections
Projected centerlines don’t meet for SCW
5m then snap
5 meters
> 5m no snap
Shape points marking end of unprojected
centerline
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Projected centerlines don’t meet for DCW
Specs - Offset Intersections
Shape point marking end of un-projected
centerline
Shape point marking end of un-projected
centerline
5 meters
5 meters
5 meters
5 meters
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Specs - Curved Roads
Curved intersection Clear distinction of
importance Smooth course through
intersection
A
B
C
Note: Often A and B will have the same name, and a more important FCC and
ACC than C.
In this example, A and B represent a road that is of higher importance than road C. If the
physical characteristics of the more important road indicate that it continues smoothly
through the intersection, the roads should be represented as shown.
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Specs - Corners
A road that goes around a corner where the road casings form a sharp corner, and the road name, address directionality / parity / format / etc. or some other segment attribute changes at the corner is added as shown. If no attributes change, then only a shape point is needed at the corner.
Node
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Specs - Corners
Node
Shape points
A road that goes around a corner where the road casings form a curved corner, and the road name, address directionality / parity / format / etc. or some other segment attribute changes at the corner is added as shown. If no attributes change, the node is not needed.
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Terms
– Bulb = circular turn around area
– Stem = portion of dead end road that leads to the bulb
Bulb must have minimum of 3 segments
Stem can be divided (>40 meters long)
Stem can be undivided ( 40 meters long)
Specs - Dead ends/ Cul-de-sacs
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Specs - Dead ends/ Cul-de-sacs
Divided stem with divided
bulb
Divided stem with undivided bulb 25 m
40 m“Stem”
Divider
“Bulb”
“Stem”
Divider
“Bulb”
40 m
25 m
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With loop– Legal or physical divider
– U-turn
– 25 meters
Loop is digitized since there is a physical divider and the diameter of the “bulb”, measured along the general direction of the road, is 25 meters (~ 82
feet)
Specs - Dead ends/ Cul-de-sacs
25 m
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The same rule applies if the divider at the end of the road is legal
Specs - Dead ends/ Cul-de-sacs
With loop– Legal or physical divider
– U-turn
– 25 meters 25 m
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Specs - Dead ends/ Cul-de-sacs
Without loop– Centerline to end
25 m
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Cul-de-sac must have only one stem
Specs - Dead ends/ Cul-de-sacs
25 m 25 m
Circular turnaround
area #2
Circular turnaround
area #1
A31
A41
A61
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Specs - Bumps
Resembles driveway Same street characteristics 40 meters long Road bulge
– Long
– Bubble-like
– Loop
10 - 28 Elm Street
10 12 14
16 22
18 20
24 26 28
Example illustrates the correct centerline representation for a spur “bump” in cases where the spur centerline is 40 meters ( 130 feet) in length.
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Specs - Bumps
Along roads At intersections
Example illustrates the correct centerline representation for a loop “bump” in cases where the loop centerline is 40 meters ( 130 feet) in length.
10 - 28 Elm Street
10 12 14
16 22
18 20
24 26 28
Example illustrates the correct centerline representation for a corner spur “bump” in cases where the spur centerline is 40 meters ( 130 feet) in length.
40 42 44 46
50
54
58
60
62
64
48 52
56
40 - 64 Oak Street
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Specs - Connecting Roads
All isolated connectors will be added– One way
– Bi-directional
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Specs - Connecting Roads
Curved connecting roads– Gradually depart one carriageway
– Gradually enter the opposing side
The angle the connecting road departs the carriageway () should be 30°. The angle the connecting road joins the opposing carriageway () should also be 30°.
The U-turn channel is considered to
begin at this point
Solid channelizing lines Broken lane line markings
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Specs – Single-Point Urban Interchanges
SPUIs Phoenix Interchanges All travel paths digitized
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Single digitized cross street– the center lines for ramps
carrying right turning traffic are drawn so that they meet at a valence-6 node.
• EXAMPLE
Specs – Single-Point Urban Interchanges
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Double digitized cross street– corresponding ramp center lines
are drawn so they form a diamond within the box defined by the intersection of the dual carriageway and limited-access highway center lines
• EXAMPLE
Specs – Single-Point Urban Interchanges
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Specs - Highway Ramps
If the exit ramp is well defined, then angle between the ramp centerline and the limited-access highway centerline should reflect the angle between the real-world exit ramp and the real-world highway.
Projected portion of
ramp centerline
begins at this point
Broken lane line markings
Channelizing lines
Channelizing lines
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Specs - Highway Ramps
Channelizing
lines
Auxiliary lane
Projected portion of
ramp centerline begins at this point
Broken lane line markings
Channelizing lines
If the ramp is accessed by means of an auxiliary lane that runs parallel to the highway, then the ramp centerline follows the center of the traversable portion of the real-world ramp until the point where the channelizing lines end and the broken lane line markings begin. At that point, the ramp centerline is projected so that it intersects the highway centerline at an angle 10.
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Specs - Highway Ramps
Weaving intersections – A section of a highway where an entrance ramp is followed closely
by an exit ramp such that the paths of vehicles entering and exiting the highway cross each other
– In the event that the length of the “weaving section” is too short to allow the departing and entering road center lines to intersect the highway center line at the angles described in the previous slide, the angles between the ramp and highway center lines are increased up to a maximum angle of 30°.
– The angles are only increased by the minimum amount necessary to ensure that the ramp center lines do not cross and that the nodes where the ramps meet the highway are separated by a highway segment
– The exit ramp angle is only increased once the entrance ramp angle has reached 30°.
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Projected portion of ramp
centerlines begins at these
points
Specs - Highway Ramps
This is an example of a weaving intersection that is too short to allow the ramp centerlines to intersect the highway at the desired angle – i.e. 10 in this case. In
order to ensure that the ramp centerlines do not cross and at least one highway segment separates the nodes where the ramp centerlines intersect the highway centerline, the entrance ramp angle in this example has been increased to 30,
while the exit ramp angle has been increased to 20.
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Specs - Highway Ramps
In cases where closely spaced exit or entrance ramps depart from the same entrance or exit lane, or from a shared open area where the lanes are defined solely by broken painted lines, one valence-3 node is created at the exit from the highway, followed with a fork at the point where both exit lanes separate.
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In cases where the intersections of the respective centerlines with the highway are spaced less than 5m from each other, they are contracted into one valence-4 node.
Specs - Highway Ramps
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Specs - Highway Ramps
Valence-3 nodes
100 m
In cases where two consecutive exit ramps whose projected centerlines intersect a limited-access highway within a distance of 100m ( 328 ft) of each other, but which are not accessed from a shared open area where the lanes are defined solely by broken painted lines are drawn so that they depart the limited-access highway at separate valence-3 nodes.
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Specs - Blocked Intersections
Internal legal or physical barriers restrict the connectivity between entering and departing roads
Represented by drawing a centerline for each of the paths defined by the barriers
A
B
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Specs - Dual Carriageway Crossovers
All left turns between intersecting dual carriageways occur via left hand turn channels
Crossover point occurs within 5 meters of the through DCW centerline.
Crossover point
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All left turns between intersecting dual carriageways occur via left hand turn channels
Crossover point occurs more than 5 meters from the through DCW centerline
Specs - Dual Carriageway Crossovers
Crossover point
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All left hand turns are not made via left hand turn channels.
Angle of the left turns must be 90°, therefore a small segment needs to exist even if this results in segments crossing over the median.
Specs - Dual Carriageway Crossovers
Crossover point
60 taper angle
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Specs - Stacked Roads
Sometimes, it is very common to have roads running above each other (on different levels). These are called stacked roads. When stacked roads are encountered, it is necessary to create separate centerlines representing each appropriate level
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Specs - Stacked Roads
Often share the same X,Y location Differ only by GSC/Brunnel Information Parallel centerlines offset by 3 meters- Ensures proper representation Configuration of the segments depends on- Number of carriageways in the road - How they are stacked
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Specs - Stacked Roads – GSC
Each level must carry appropriate GSC attribution relative to its position above the ground.
Where the parallel centerlines converge (where the multi level stops) intersections are often created that do not necessarily reflect reality. Appropriate maneuvers and/or GSC/Brunnel attribution must be added when necessary.
Centerline illustration of a 3-level bridge. Numbers indicate GSC attribution.
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Specs - Stacked Roads
If stack has 2 decks, configuration depends upon the number of carriageways in the roads
2 options - Single carriageway roads over single carriageway roads - Dual carriageway roads over either single or dual carriageway
roads. A stacked dual carriageway is a multi-deck road in which at least
one deck carries a dual carriage road. Generally, the upper dual carriageway is placed in the correct position.
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Specs - Stacked Roads
Single carriageway over single carriageway: None of the two roads are actually placed at the exact location. Each
road is placed a bit offset from the actual centerline.
(actual centerline)
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Specs - Stacked Roads
Dual carriage roads in combination with single carriage roads:
1. A dual carriageway is stacked over a single carriageway: IF no carriageways are stacked directly over the single carriageway, THEN
All carriageways are captured on the correct positional accuracy.
RealityDatabase
This carriageway and this carriageway are offset
Top level
Bottom level
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Specs - Stacked Roads
2. A dual carriageway is stacked over a single carriageway:– IF one carriageway is stacked directly over the single carriageway, THEN
– The dual carriageway is placed in the correct position and the SCW is
placed outside its immediately higher neighbor.
Dual carriage roads in combination with single carriage roads:
This carriageway and this carriageway are right on top of each other
Top level
Bottom level Remember this distance is 3 meters
Reality Database
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Specs - Stacked Roads
Dual carriage roads in combination with single carriage roads:
1. A single carriageway is stacked over a dual carriageway: IF the single carriageway is stacked directly over one carriageway of the
dual carriageway, THEN The dual carriageway is placed in the correct position; the single
carriageway is placed outside its immediately lower neighbor.
This carriageway and this carriageway are right on top of each other
Top level
Bottom levelRemember this distance is 3 meters
Reality Database
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Specs - Stacked Roads
Dual carriage roads in combination with single carriage roads:
4. A single carriageway is stacked over a dual carriageway: IF the single carriageway is NOT stacked directly over one
carriageway of the dual carriageway, THEN All carriageways are captured in the correct positional
accuracy.
This carriageway and this carriageway are offset
Top level
Bottom level
Note: This would be the representation if in reality the single carriage was in between and above the dual.
Reality Database
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Specs - Stacked Roads
Dual carriage roads in combination with dual carriage roads:
Generally, the uppermost deck that carries a dual carriageway road is
represented with the best positional accuracy.
The carriageways of all other decks are displayed as necessary.
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Specs - Stacked Roads
Dual carriage roads in combination with dual carriage roads:
1. A dual carriageway is stacked directly over another dual carriageway: The upper DCW gets the correct position. Each carriageway of the lower multi-carriageways is placed outside its
immediately higher neighbor.
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Specs - Stacked Roads
Dual carriage roads in combination with dual carriage roads:
2. A dual carriageway is stacked over another dual carriageway, but no carriageway is stacked directly over another carriageway:
All carriageways are located at the exact position.
Top level
Bottom level
These carriageways and these carriageways are offset.
Reality Database
Note: This would be the representation if the top DCW was larger and therefore had a bigger separation between centerlines.
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Methods - Stacked Roads
Dual carriageway is the uppermost deck of the stack:This means that the lower decks can contain dual or single
carriage roads.1. Always start by placing the dual carriage way in its correct position.2. Then work your way down:3. If the next lower road is located directly under one of the
carriageways, place it outside its immediately higher neighbor.4. If the next lower road is NOT located directly under one the
carriageways, place it in its correct location.5. Keep working your way down until you have placed the lower deck.
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Methods - Stacked Roads
A dual carriageway road is the lowermost deck of the stack:This means that the higher decks only contain single carriage
roads:1. Start by placing the dual carriageway in its correct location. Then
work your way up:2. If the next higher road is located directly over one of the
carriageways, place it outside its immediately lower neighbor.3. If the next higher road is not located directly over one of the
carriageways, place it in its correct location.4. Keep working your way up until you have placed all the stacks.
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Methods - Stacked Roads
If a dual carriageway is in the middle, start with the highest dual carriageway:
This means that the higher decks only contain single carriage roads. The lower decks can be single or dual.
1. Start by placing the dual carriageway in its correct position. Then work your way down:
2. If the next lower road is located directly under one of the carriageways, place it outside its immediately higher neighbor.
3. If the next lower road is not located directly under one the carriageways, place it in its correct location.
4. Keep working your way down until you have placed the lowest deck.
Continued on next slide…
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Methods - Stacked Roads
If a dual carriageway is in the middle, start with the highest dual carriageway:
1. Next, look at the decks above the dual carriageway. 2. If the next higher road is located directly over one of the
carriageways, place it outside the outermost of the already displayed carriageways.
3. If the next higher road is not located directly over one of the carriageways, place it in it is correct location.
4. Work you way up until you have placed the highest deck.
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Large Intersections
Intersections involving 5 or more road chains Smooth centerlines and reduced complexity important Centerlines are drawn according to spec Un-projected centerlines connected through intersection
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3 or more projected centerlines would pass within 5 meters of each other and create a triangle with at least 2 sides measuring <1 meter, then the nodes are moved so they meet at a single node
Only road centerlines within the intersection are moved Centerlines within road casings are not moved
Large Intersections
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Large Intersections
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Symmetric Forks
No legal divider In the case of a fork without a legal
divider, valence-3 junction occurs where the centerlines of the branches of the fork intersect with the incoming road at one point
A fork in the road is digitized by projecting the branches of the fork until they intersect with the centerline of the incoming road
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Legal Divider In the case of a fork with an
extended legal divider, the valence-3 junction is moved on the incoming road to the point where the legal divider starts.
The geometry is digitized so that the angle α is between 20° and 90°, and that the curve between points a and b, and between a and c, does not change.
Symmetric Fork with legal separation
Symmetric Forks
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Long Legal Divider In the case where the length of the
legal dividers would cause the angle α to become smaller than 20°, the centerlines of the legally separated branches are digitized northwards of the points d and e.
The connecting geometry between point a and d and point a and e has a taper angle of 60°.
Symmetric Fork with long legal separation
Symmetric Forks
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Asymmetric Forks
No Legal Divider In the case of an asymmetric fork, the projected centerline of the
branches do not intersect with the incoming centerline in one point.
In such a situation the valence 3 junction is digitized in the point on the centerline of the incoming road that is the first intersection of the projected centerlines of the branches along the incoming road.
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Asymmetric Forks
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Long Legal Divider In the case where there is a long
legal separation on the incoming road, the geometry of the fork is digitized applying the rules lined out in “Symmetric Forks with Long Legal Divider” (slide 176) for each branch separately
Asymmetric Forks
Asymmetric fork with long legal separation
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Semi-Permeable Dividers
Semi-permeable dividers will be considered as permeable dividers as long as they don’t rule out any of the directions following the decision point (A).
AThe semi-permeable part of the divider is not considered in the geometry because it doesn’t exclude traffic from one of the directions at the decision point.
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Semi-Permeable Dividers
As soon as a semi permeable divider restricts traffic from one of the directions the related decision point gives access to, it is considered as an impermeable legal divider (B).
B
Semi-permeable divider considered as an impermeable legal divider because traffic on the left side of this divider is excluded from taking the southeast branch of the fork.
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Asymmetric Road Width Changes
According to centerline rules, there would be a zig-zag when the prepared road intended for through traffic is extended by one or more lanes at one side .
There is no corresponding zig-zag in reality. A zig-zag in the data can have unwanted effects on
applications. A smooth transition is digitized between the centerline before
and the centerline after the lanes change.
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Asymmetric Road Width Changes
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Length of the transition segment depends on the number of lanes being added or removed.
Asymmetric Road Width Changes
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Asymmetric Road Width Changes
In the case where the road width change occurs in a curve in the road, the connection between the two centerlines is digitized so that the curve does not change direction.
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Temporary road width changes typically occur in entrance to exit situations as discussed in Weaving Intersections (slide 145)
Also occur in cases of ‘slow vehicle lanes’ and the like Temporary road width changes on limited access highways are
not taken into account if they are shorter than 3 km (~2 miles)
Asymmetric Road Width Changes
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Asymmetric Road Width Changes
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Exercises
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Exercises
Physical Barrier Legal Median to allow for turn lane
How would you digitize this?
No barrier on this side
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Exercises
Where would we measure to see if this should be captured?
>7.5 m
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Exercises
26.5 meters
How would this be added?
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Exercises
Street is offset by 5 meters
How would you digitize this?
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Questions