HCM Guidance for Alternative Intersections

HCM GUIDANCE FOR ALTERNATIVE INTERSECTIONS

Michael Armstrong, E.I.

2015 FSITE WINTER WORKSHOP:

INNOVATIVE INTERSECTION/INTERCHANGE DESIGN APPLICATIONS

HCM 2010 “Major Update”

Alternative Intersections & Interchanges procedures to

be included in NCHRP 03-115 “Production of a Major

Update to the 2010 Highway Capacity Manual”

Target publication date within 2015

Extensive discussions at 2015 TRB Annual Meeting last

month (January 11-15, 2015)

Project Overview

McTrans™ involved

with Task 5

Updates to

calculation engine

and user interface

in HCS 2010™

Streets under

development

FHWA-HRT-13-083

New HCM Content & Organization

Ch. 23 (formerly Ch. 22): Ramp Terminals & Alternative Intersections

Part A: Concepts

Part B: Interchanges (Diamond, Parclo, SPUI, DDI)

Part C: Alternative Intersections (MUT, RCUT, DLT)

Ch. 34: Interchange Ramp Terminals Supplemental

Example Problems (8 new examples added)

Operational Analysis for Interchange Type Selection

O-D and Turning Movements

New HCM Content & Organization

Ch. 30 (formerly Ch. 29): Roundabout Corridors

Urban Streets Supplemental material; similar procedure

Incorporates new inputs such as inscribed/central island

diameter, circulating speed, median type, etc.

Performance measures include segment FFS, running time,

roundabout influence area, mid-segment access point delay,

geometric delay, v/c ratio, facility travel time, travel speed, etc.

Level of Service based on Percent BFFS

Displaced Left Turn (DLT) Intersections

Overview of new procedures

Example: Partial DLT

Signalized Intersections procedure (formerly Ch. 18,

now Ch. 19) used for all three intersections to obtain

performance measures, including Control Delay

Urban Streets procedure (formerly Ch. 17, now Ch. 18)

used for both segments to obtain flow-profile analysis

and performance measures

Demand input: “overall” O-D three separate TMC’s

DLT Intersections

DLT Intersections

LOS based on Experienced Travel Time (ETT):

summation of Control Delay(s) for each O-D

𝐸𝑇𝑇𝑖 = 𝑑𝑖 𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗

Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”, Draft Chapter 23

DLT Intersections


To overcome issue of allowing major street through-plus-right

and opposing protected-left movements in the same phase:

crossover signals must be offset so left turns theoretically

experience zero delay at main intersection (P = 1.00)

Suggested procedure for calculating offset time included

Treat displaced lefts as if they don’t exist at main intersection

DLT Intersections

Impossible to re-create

actual phasing scheme

DLT Intersections

WB CrossoverEB Crossover Main Intersection


An EB/WB major street that

intersects a NB/SB minor street

at an isolated location has high

left-turn demands and several

failing movements. Other

movements are near capacity

and there is concern about

future traffic growth. Would

this conventional intersection

function better as a DLT? Control = fully actuated

PHF = 0.92

Lost Time = 2.0 s

Ext. of Eff. Green = 2.0 s

RTOR = none

Parking = none

Buses = none

Bikes, Peds = none

680 75720

709700

81

60060 460

69

447545

Delay: 64.1 s/veh

LOS E


3rd Int

WB Crossover

1st Int.

EB Crossover

2nd Int.

Main Intersection

350’ 350’

EBT,

EBR

790

EBL

700WBT,

SBR,

NBL

1285

EBT

709

EBR

81

NBL

680

NBR

75

NBT

720

SBR

60

SBL

460

SBT

600

WBR

69

WBT

545WBL

447

WBT,

WBR

614

EBT,

NBR,

SBL

1244

Offset: 45 s Offset: 45 s


MovementO-D,

veh/h

Individual TMC's, veh/h Control Delay, s/veh ETT*

VolumeInt. 1 Int. 2 Int. 3 Int. 1 Int. 2 Int. 3

EBL 761 761 22.5 17,123

EBT 437 859 437 1,352 0.4 41.9 2.5 22,034

EBR 422 422 42.5 17,935

WBL 486 486 25.7 12,490

WBT 340 1,397 340 667 4.0 29.3 0.4 15,817

WBR 328 328 29.7 9,742

NBL 739 739 23.7 17,514

NBT 439 439 19.8 8,692

NBR 425 425 19.8 8,415

SBL 500 500 26.2 13,100

SBT 364 364 23.4 8,518

SBR 353 353 23.5 8,296

Intersection ETT, s/veh 𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗 28.5 s/veh (55% improvement, LOS E to C)

Procedure is essentially an “extension” of the existing

Signalized Intersections and Urban Streets HCM

procedures with a few minor additions

Best suited for facilitating comparison to existing

conventional intersections

Data collection at existing DLT intersections may be

problematic based on the new procedure’s O-D demand

input requirement

DLT Intersections Summary

U-Turn Intersections (MUT, RCUT)


Example: MUT

Example: RCUT

MUT & RCUT Intersections

Same concept of converting “overall” O-D demands

to three separate TMC’s

Ch. 19 and Ch. 18 procedures again handle

performance measures for the three signalized

intersections and two segments, respectively

TWSC procedures (now Ch. 20) used for unsignalized

U-turns, facilitates “hybrid” analysis


Type # Legs Main Intersection U-Turn Intersections

MUT Four Signalized Signalized

MUT Four Signalized Stop Signs

MUT Three Signalized Stop Signs

RCUT Four Signalized Signalized

RCUT* Four Stop Signs or Merges/Diverges Stop Signs or Merges/Diverges

RCUT Three Signalized Signalized

RCUT* Three Stop Signs or Merges/Diverges Stop Signs or Merges/Diverges


*Check for optional

weaving analysis

(now Ch. 13) for

RCUT intersections

with merges

No weaving

analysis necessary

Weaving analysis

recommended



U-turn saturation flow adjustment factor (fUT)

depends on median width


fLT = 0.95 (conventional intersections)


Dt = distance from main intersection to U-turn

Df = distance from U-turn to main intersection

a = delay by acceleration/deceleration in movements with merges

𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓

1.47 ∗ 𝐹𝐹𝑆+ 𝑎 𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇

ETT includes “Extra Distance Travel Time” (EDTT) for

movements using U-turns:


EDTT = (U-Turn) – (Direct LT)


LOS criteria again depends on ETT – but only for each

O-D movement (rather than intersection as a whole)

Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major Update”,

Draft Chapter 23

MUT Configuration

East U-TurnWest U-Turn Main Intersection

RCUT Configuration

East U-TurnWest U-Turn Main Intersection

Example: MUT

A 4-leg MUT with stop signs at its U-turn crossovers is located in a suburban area. The N/S

major street has two through lanes with shared right-turn lanes at the main intersection,

while the minor street has one through lane and one exclusive right-turn lane at each

approach. Both U-turn crossovers have a single lane.

Segments = 800’

Storage bays = 500’

PHF = 0.95

FFS = 50 mi/h

HV = 2%

Grades = none

Peds = 100/h

RTOR = restricted

Yellow = 4 sec

Red = 1 sec

Signal = actuated, un-

coordinated280 60

700

40070

200

120080 50

50

80300

Determine ETT and LOS for all 12 O-D movements.

Example: MUT

1st Int.

South U-Turn

3rd Int.

North U-Turn

2nd Int.

Main Intersection

SBL,

SBT,

SBR

1330

EBL,

SBL

120

NBL,

NBT,

NBR

1040

EBT

400

EBR, EBL

270

WBT

300

WBR, WBL

130WBL,

NBL

360

SBR,

NBL

360

SBT,

WBL

1330

NBR,

SBL

110

NBT,

EBL

1050

Example: MUT

1st Int.

South U-Turn

3rd Int.

North U-Turn

2nd Int.

Main Intersection

SBL,

SBT,

SBR

1400

EBL,

SBL

126

NBL,

NBT,

NBR

1090

EBT

421

EBR, EBL

284

WBT

316

WBR, WBL

137WBL,

NBL

379

SBR,

NBL

379

SBT,

WBL

1400

NBR,

SBL

116

NBT,

EBL

1110

Example: MUT


𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇

𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓

1.47 ∗ 𝐹𝐹𝑆

=800 + 800

1.47 ∗ 50

= 21.8 𝑠/𝑣𝑒ℎ

Example: MUT

𝐸𝑇𝑇𝐼 = (𝐸𝑇𝑇𝑗 ∗ 𝑣𝑗) 𝑣𝑗 ~ 24.4𝑠

𝑣𝑒ℎ, 𝐿𝑂𝑆 𝐶


Example: RCUT

A 4-leg RCUT with merges at the U-turns has its major

street running E/W and is located in a rural area.

Segments = 2,000’

Storage bays = 300’

PHF = 0.92

FFS = 60 mi/h

HV = 0%

Grades = none

200 20090

800

120

220

50100 100

110

180

500

Determine ETT and LOS for all 12 O-D movements.

Example: RCUT

3rd Int.

East U-Turn1st Int.

West U-Turn

2nd Int. Main Intersection

EBL, EBT, EBR

1140

NBL, NBT

290

SBL, SBT

150

EBL

120

WBR

200

NBL, NBT, NBL

490

WBL, WBT, WBR

790

SBL, SBT, SBL

250

WBT

700

WBL

180

EBT

900

EBR

270

Example: RCUT

3rd Int.

East U-Turn1st Int.

West U-Turn

2nd Int. Main Intersection

EBL, EBT, EBR

1240

NBL, NBT

315

SBL, SBT

163

EBL

130

WBR

217

NBL, NBT, NBL

533

WBL, WBT, WBR

859

SBL, SBT, SBL

272

WBT

761

WBL

196

EBT

978

EBR

293

Example: RCUT

No weaving

analysis necessary

Weaving analysis

recommended


Major street

through vs. minor

street through/left:

(1240, 163)

(859, 315)

(978, 533)

(761, 272)

No weaving

analyses

necessary!

Example: RCUT

Merging maneuvers are assumed to incur zero delay and no

significant delay expected from potential weaving segments,

therefore the only movements experiencing any control delay

are major street left turns at the main intersection

Using TWSC procedures (Ch. 20):

EB Left at Int. 2

v/c = 0.18

95th %ile Queue = 16.5’

Control Delay = 11.2 s/veh

WB Left at Int. 2

v/c = 0.35

95th %ile Queue = 39.5’

Control Delay = 15.0 s/veh

Example: RCUT

𝐸𝐷𝑇𝑇 =𝐷𝑡 + 𝐷𝑓1.47 ∗ 𝐹𝐹𝑆

+ 𝑎

=2,000 + 2,000

1.47 ∗ 60+ 15

= 60.4 𝑠/𝑣𝑒ℎ

=2,000 + 2,000

1.47 ∗ 60+ 10

= 55.4 𝑠/𝑣𝑒ℎ

NBT and SBT

NBL and SBL

Example: RCUT

Source: NCHRP 3-115 “Production of the 2010 Highway Capacity Manual Major

Update”, Draft Chapter 23

Example: RCUTMovement 1st Int. 2nd Int. 3rd Int. EDTT Total LOS

EBL 0.0 11.2 - - 11.2 s/veh B

EBT 0.0 0.0 0.0 - 0.0 s/veh A

EBR 0.0 0.0 - - 0.0 s/veh A

WBL - 15.0 0.0 - 15.0 s/veh B

WBT 0.0 0.0 0.0 - 0.0 s/veh A

WBR - 0.0 0.0 - 0.0 s/veh A

NBL 0.0 0.0 0.0 55.4 55.4 s/veh E

NBT - 0.0 0.0 60.4 60.4 s/veh E

NBR - 0.0 0.0 - 0.0 s/veh A

SBL 0.0 0.0 0.0 55.4 55.4 s/veh E

SBT 0.0 0.0 - 60.4 60.4 s/veh E

SBR 0.0 0.0 - - 0.0 s/veh A

MUT & RCUT Intersections Summary

Plenty of variation in terms of configuration types

Does not produce performance measures for intersection

as a whole – only individual O-D movements

Data collection at existing MUT or RCUT intersections

nearly impossible based on procedure’s O-D input

requirement

Diverging Diamond Interchanges (DDI)


Example: DDI with signal control

DDI/DCD Interchanges

Very similar to existing conventional diamond interchange

procedure (formerly Ch. 22)

Certain movements can be signal- or yield-controlled;

includes new gap-acceptance model

New external lane utilization factors based on internal

lane configuration

New additional lost time adjustments based on clear-zone

widths and location of conflict points


New saturation flow adjustment factors

Field research showed that

saturation flows at actual DDI’s

were over-predicted by 8.7%

Therefore, fDDI = 0.913



New Lost Time equations



New procedure for capacity of yield-controlled movements (similar to TWSC)

Regime 1: Blocked by conflicting platoon when the conflicting signal has

just turned green, resulting in zero capacity for the turning movement

Regime 2: Gap acceptance in conflicting traffic after the initial platoon

has cleared, with gap acceptance controlled by critical gap, follow-up

time, and conflicting flow rate

Regime 3: No conflicting flow when the conflicting signal is red, resulting in

full capacity, controlled by follow-up time of the yield-controlled approach



ETT now used to determine LOS for all interchange types

𝐸𝑇𝑇 = 𝑑𝑖 + 𝐸𝐷𝑇𝑇 𝐸𝐷𝑇𝑇 =𝐷𝑡

1.47 ∗ 𝑣𝐷+ 𝑎


Example: DDI (Signalized)

The interchange of an

arterial at a freeway is a

DDI with signals controlling

movements from the

freeway onto the arterial.

Movements onto the

freeway from the arterial

are free-flowing

Determine the delays,

ETT and LOS.



Closely spaced intersections = none

Signals = pre-timed

RTOR = none

Travel path radii = 75’ RT, 150’ LT

HV = 5%

PHF = 0.95

Start-up lost time = 2 sec

Extension of effective green = 2 sec

Parking, buses, bicycles, peds = none

Cycle length = 70 sec

Arterial FFS = 35 mi/h

Operating speed = 25 mi/h

Source: NCHRP 3-115 “Production of the

2010 Highway Capacity Manual Major

Update”, Draft Chapter 34


Source: NCHRP 3-115 “Production of the 2010 Highway

Capacity Manual Major Update”, Draft Chapter 34



Draft Chapter 34







Draft Chapter 34



Questions?

Stay up to date with HCM 2010 Major Update:

http://sites.kittelson.com/HCQS/Announcements

Check for periodic HCS 2010™ updates:

http://mctrans.ce.ufl.edu/mct/

What’s Next?

FHWA task work order to incorporate freeway-arterial

interactions (unite interrupted and uninterrupted flow)

1. How does an oversaturated off-ramp affect

freeway operations?

2. How does an oversaturated on-ramp affect

interchange operations?

Recommended changes to procedures under

development – stay tuned

Documents

HCM Guidance for Alternative Intersections