Multimodal 54 Meeting
October 17, 2016
Designing for Progression on NC-54
Joe Hummer, Staff Engineer, M&S
Designing for Progression
• Progression is one of the best things we do
• Especially in NC with random block lengths
• And aversion to one-way streets
• Difficult to establish after road network is in place
• Long cycle lengths
• Favor one direction
• Lead/lag, with flashing yellow arrows if needed
• Problems with each of those
• Much easier if we build progression opportunity
into the system
2
Transportation
One-Way Progression
is Easy
• Just choose a speed
• Set start of green
(offset) on left edge
of band
• Bandwidth = smallest
green
3
Transportation
Two-Way Progression is Hard
4
Transportation
Classic Two-Way Progression Plans
• Simultaneous
• All offsets are equal
• Use with short signal spacing
Roess, Prassas,
and McShane, 4th
ed., Figure 26.24
5
Transportation
Classic Two-Way Progression Plans
• Alternate
• Offsets at every other signal (first, third, fifth, etc.) are equal
• Offsets at the signals in between (second, fourth, sixth, etc.) are
exactly half the cycle length
• Vehicles move from one signal to next in half a cycle
• Use with longer signal spacing
Roess, Prassas,
and McShane, 4th
ed., Figure 26.22
6
Transportation
What Are “Short” and “Long” Signal Spacings?
• Use classic equation for two signals:
Efficiency = 0.5 – (L / (S * C))
• Where L is distance between signals in feet, S is speed in ft/sec, and C is
cycle length in sec
• Efficiency is proportion of cycle used by band
• Given desired efficiency, can solve backward for L
• For 40% efficiency:
Speed,
mph
25
30
35
40
35
40
45
50
55
7
Speed,
fps
37
44
51
59
51
59
66
73
81
Cycle, sec
80
80
80
80
150
150
150
150
150
Alternate
Simultaneous
Low
High
Limit, ft
limit, ft limit, ft
293
1173
1760
352
1408
2112
411
1643
2464
469
1877
2816
770
3080
4620
880
3520
5280
990
3960
5940
1100
4400
6600
1210
4840
7260
Random
flow, ft
2640
2640
3960
3960
3960
3960
5280
5280
5280
Transportation
Where Simultaneous or Alternate Plans Will Not Work,
Use a Synchronized Street
• Perfect progression both directions, any speed, any spacing
• Good for safety, peds, access
• Capacity limit on cross street (~ 25,000 AADT)
• Need lateral (>45 ft radius) and longitudinal (>400 ft) room for crossovers
8
Transportation
But Making Every Arterial
a Synchronized Street is Impossible
• Side street capacity exceeded
• Cost
• Impact
• Public relations problems
• We need to be smart
• Put synchronized streets where needed for
progression
9
Transportation
First, An International Arterial Example, Eh
• Toronto, Ontario
• Tearing down the elevated freeway, to better connect downtown to the lake
10
Transportation
Crossing Pedestrians While
Still Moving Traffic
Example
Proposed 8-lane divided street, 3000+ vph WB,
1500+ vph EB, heavy pedestrian crossing demand
Conventional v/c
0.96
0.91
1.00
1600’
0.64
1300’
1400’
1000’
0.59
Demands, vph
EB left
480
120
60
WB left
120
60
110
NB left & th
210
310
140
SB left & th
70
90
100
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Transportation
No Progression Eastbound
120-sec cycle, 30 mph progression speed, dead zone is 528’ to 2112’
Time,
sec
90
60
30
0
0
800
1600
2400
3200
4000
4800
Distance, ft
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Transportation
Proposed
Solution
Proposed
Solution
Synchronized street at second and fourth intersections, others remain conventional
Proposed v/c
0.96
0.91
0.78
1600’
1000’
0.54
1400’
0.59
1300’
Crossovers
Great two-way progression, acceptable v/c ratios, extra midblock ped crossings
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Transportation
Great Progression Both Directions
“Progression score” goes from -22 to +9
Time,
sec
90
60
30
0
0
800
1600
2400
3200
4000
4800
Distance, ft
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Transportation
Back in NC: What to Do About NC-54?
An interchange, eight signalized intersections, then a grade-separated intersection.
15
Transportation
NC-54 Currently From I-40 to Hamilton
Not Including US-15/501
Direction: WB
Speed limit, mph: 45
Signal
I-40 EB ramps
Farrington
Huntingridge
East Barbee
Meadowmont
West Barbee
Burning
Hamilton
Dist. from
last, ft
>5280
370
2100
5700
1040
1930
850
1560
Subtotal:d
13550
Average points per mile:
16
Roadway: NC-54
Cycle length, sec: 150
Cumul.
Type of
dist, fta
signal b
Full
Full
Full
Full
Full
Full
Full
Full
2970
Phases
3
4
3
4
4
3
3
3
Simultaneous Alternate Alternate Random
limit, ft
low limit, high limit, flow limit,
ft
ft
ft
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
Distance c
Too long
Sweet
Dead
Too long
Sweet*
Dead
Sweet
Dead
Score
-1
1
-4
-2
0
-4
2
-4
-12
-3.7
Transportation
NC-54 as Synchronized Street
Direction: WB
Speed limit, mph: 45
Signal
I-40 EB ramps
Farrington
Crossover
Huntingridge
Crossover
East Barbee
Crossover
Meadowmont
Crossover
West Barbee
Crossover
Burning
Crossover
Hamilton
Dist. from
last, ft
>5280
370
1500
600
5100
600
570
470
1330
600
475
375
960
600
Subtotal:d
13550
Average points per mile:
17
Roadway: NC-54
Cycle length, sec: 150
Cumul.
Type of
a
signal b
Half
Full
Half
Half
Half
Half
Half
Half
Half
Half
Half
Half
Half
Half
dist, ft
Phases
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Simultaneous Alternate Alternate Random
limit, ft
low limit, high limit, flow limit,
ft
ft
ft
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
Median u-turn at Farrington, parclo B at I-40 EB ramps.
Distance c
Too long
Sweet
Not too long
Second member
Not too long
Second member
Not too long
Second member
Not too long
Second member
Not too long
Second member
Not too long
Second member
Score
0
3
5
0
5
0
5
0
5
0
5
0
5
0
33
13.4
Transportation
Discussion of Synchronized Street
• Much better progression, score -4 to 13
• v/c improved too
• Eight junctions altered, at least $40 million
• Two at $8 million, six at $4 million
• Room for crossovers
• West of Hamilton (810’)?
• Between Burning Tree and West Barbee (850’)?
• Between Meadowmont and East Barbee (1040’)?
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Transportation
NC-54 as Partial Synchronized Street
Direction: WB
Speed limit, mph: 45
Signal
I-40 EB ramps
Farrington
Crossover
Huntingridge
Crossover
East Barbee
Crossover
Meadowmont
West Barbee
Burning
Crossover
Hamilton
Dist. from
last, ft
>5280
370
1500
600
5100
600
570
470
1930
850
960
600
Subtotal:d
13550
Average points per mile:
19
Roadway: NC-54
Cycle length, sec: 150
Cumul.
Type of
dist, fta
signal b
Full
Full
Half
Half
Half
Half
Half
Half
Full
Full
Half
Half
Phases
3
2
2
2
2
2
2
2
3
3
2
2
Simultaneous Alternate Alternate Random
limit, ft
low limit, high limit, flow limit,
ft
ft
ft
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
990
3960
5940
5280
Median u-turn at Farrington.
Distance c
Too long
Sweet
Not too long
Second member
Not too long
Second member
Not too long
Second member
Sweet
Sweet
Not too long
Second member
Score
-1
3
5
0
5
0
5
0
2
2
5
0
26
10.4
Transportation
Discussion of Partial Synchronized Street
• Progression score 13 to 10
• v/c 0.68, 0.63, and 0.65 at three junctions left
conventional
• Saved ~$16 million compared to full
synchronized street
• Still need crossovers at some tight spots
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Transportation
What to do About NC-54 at US-15/501?
Grade-Separated Intersection
• Intersections with at least one bridge
• Neither intersecting route is a freeway
• Both streets can have signals, progression
• Higher cost than at-grade
• Higher capacity that at-grade
• We have over 200 of these in NC, with more on
the way
Transportation
What is Wrong with This Design in This Spot?
Parclo A at Dawson/McDowell and Western/ML King, Raleigh
Transportation
What is Wrong with This Design in This Spot?
Parclo A at Dawson/McDowell and Western/ML King, Raleigh
High speed
Peds
No metering
Progression
Too much ROW
Transportation
New Designs
Single-Point and Synchronized Street
From Dennis Eyler, SRF Consulting, Minneapolis, MN, 2011
Transportation
New Designs
Contraflow Left Intersection
Transportation
Scoring the Designs in General
26
Design
Good aspects
Poor aspects
Total score
(of 65)
Parclo A
Capacity, conflict points
Distance traveled,
progression, peds
36
Cloverleaf
Capacity, progression
wrong way potential
Distance traveled, unusual
maneuvers, cost, peds
28
Half-half
Efficient, safe, cheap, and
pedestrians
Nothing
54
Contraflow
Efficient, safe, cheap, and
pedestrians
Nothing
54
Transportation
Constraints at US-15/501 and NC-54
• Bridge ancient
• Cloverleaf poor for peds
• Loops substandard
• Heavy WB left
• Super-high ROW cost
• Sensitive environment
27
Transportation
Should US-15/501 at NC-54 Remain an Interchange?
• Cloverleaf
• Substandard loops
• Poor for pedestrians
• Parclo A
• Substandard loops
• Poor for pedestrians
• Poor for progression along NC-54
• Other interchange designs also
have serious flaws
28
Transportation
US-15/501 at NC-54 as a Half-Half
Grade-Separated Interchange
• Fits in available space
• Could use ramps in NW
and SE quadrants
• Redirected movements
are relatively low demand
29
Transportation
US-15/501 at NC-54 as a Contraflow
Grade-Separated Interchange
• May not fit quite as
well as half-half
• No extra distance
travelled
30
Transportation
Summary
• Do not settle for poor progression along NC-54
• Convert most intersections to synchronized street
• Farrington intersection as median u-turn
• I-40 interchange OK as is
• Several intersections OK as they are
• US-15/501 grade-separated intersection as half-half or
contraflow
• Reasonable costs and impacts
• Great traffic flow
• Great for pedestrians
• Reduce crashes
31
Transportation
Thank You!
32
Joe Hummer, jehummer@ncdot.gov, 919-773-2830
Transportation
For Reference Only
33
Transportation
Interchanges: Big Challenge for Progression
• Often two signals in dead zone
spacing
• Standard diamond 600-foot
spacing
• Parclo A 1200-foot spacing
• Multi-phase signals
• Standard diamond and singlepoint urban interchange 3-phase
• Tight diamond 4-phase
34
Transportation
At Least 9 Common Signalized
Service Interchange Designs in NC
• Single point
• Tight diamond
• Standard diamond
• Spread diamond
• Parclo B
• Parclo A
• Parclo AB
• Cloverleaf
• Diverging diamond
35
Transportation
Top of the Charts …Parclo B
Parclo A
36
Parclo B
Transportation
Why Parclo B is Better
37
Aspect
Parclo A
Parclo B
Progression
Two full signals at 1200foot spacing = no chance
for two-way progression
All signals only affect one
direction = perfect twoway progression
Lane utilization
All turning traffic
stacked in right lane
Left turn traffic in left
lane, right turn traffic in
right lane
Unusual
maneuvers
Left turn traffic
has to turn right
Left turn traffic stays left,
right turn traffic stays
right
Pedestrians
Each pedestrian must cross
two free-flowing ramps
All ramp crossings are
signal-controlled
Transportation
In All Other Important Respects
Parclo B and Parclo A are Equal
• Capacity
• Distance traveled
• Conflict points
• Wrong way potential
• Bridge size
• Right of way
• Extent along freeway
• Extent along arterial
38
Parclo B !
Transportation
Good Interchanges with Mediocre Progression
• Tight diamond
• Diverging diamond
• Single point
39
Transportation
Interchanges Scoring Poorly for Progression
• Standard diamond
• Parclo AB
• Spread diamond
• The worst
progression
situation in any
common
interchange
40
Transportation
New Interchanges With Top Marks for Progression
Signalized FRE
• Berry and Click, 2010
• Grown-up double roundabout
• Also great for:
• Bridge size
• Conflict points
• Lower capacity
Transportation
New Interchanges With Top Marks for Progression
Synchronized
• Contraflow, but little
chance of wrong way
movement
• Need room for loons
• Otherwise, excellent
interchange overall
42
Transportation
New Interchanges with Top Marks for Progression
Milwaukee B
• Operates like Parclo B
• High bridge cost
• Should be about half the
size of parclo B
• Excellent on efficiency and
safety measures
Transportation
Summary on Progression at Interchanges
• Have room for two loops?
• Design parclo B
• If not, have room for loons?
• Try FRE for lower demand or synchronized for higher
demand
• If not, have room and budget for two extra bridges?
• Try Milwaukee B
• Tight diamond, single point, and diverging diamond are
good overall designs with mediocre progression
• Standard diamond, parclo A, and parclo AB are mediocre
overall designs with poor progression
• Why build a spread diamond?
44
Transportation