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Innovative Intersections

Prepared for: ITE ANZ

Thursday, 5 November 2015

Presentation by Andrew O’Brien

Suite 2, 22 Gillman StreetHawthorn East , Victoria 3123

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W: obrientraff ic.com

ANDREW O’BRIEN & ASSOCIATES PTY LTD ABN: 55 007 006 037

TRAFFIC ENGINEERING TRAFFIC PLANNING ROAD SAFETY TRAFFIC IMPACT ASSESSMENTS TRANSPORT PLANNING

Diverging Diamond

Interchanges

Background

Hoddle St/Eastern Freeway

Southern Motorway/Ellerslie-Panmure Hwy, Auckland

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TRAFFIC ENGINEERING TRAFFIC PLANNING ROAD SAFETY TRAFFIC IMPACT ASSESSMENTS TRANSPORT PLANNING 3

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‘Diverging-Diamond’ Interchanges

MnDOT is constructing Diverging Diamond Interchanges

throughout the state. These interchanges:

• Cut overall traffic delays up to 60 percent

• Improve safety by eliminating standard intersection

geometrics and conflict points

• Provide better traffic operations and show some

excess capacity 20 years into the future

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Hoddle Street ‘Diverging-Diamond’ Option

Response to other’s pessimism:

• I have designed several DDIs

• Just returned from conference in USA and held

discussions with TE’s involved with DDIs

• Limited research shows safety improvements

• Design guides are just that – and are untested

• No histories of head-on crashes

• Main concern is left turn slip lanes from off-ramps

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Basic option

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Basic option – saves $25-40 m, no acquisition

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Southern Motorway/ Ellerslie-Panmure Highway

The issues:

• Long queues blocking the roundabout (rotary)

due to motorway congestion.

• Looked at a range of options to get non-

motorway traffic across the motorway

• Daniel Dryland of Resolve Group suggested a DDI

• DDI offered a way of keeping one lane free of

queues on approaches and in the roundabout

• OBT carried out various analyses and micro-

simulation that demonstrated considerable

benefits

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Interesting Intersections

MacRobertsons Bridge – signalised, semi-turbo

Turbo-roundabout WA

Beach Road, Black Rock roundabout

The ‘MUT’ – PHE/Clayton

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‘MacRobertsons Bridge northern roundabout

The issues:

• Long queues on most approaches

• Southern roundabout has DoS of about 0.7

• Delays of up to 20 minutes to get into the

southern roundabout from east, south, or west in

the AM peak

• Cyclist ‘blackspot’

The concept:

• Separate lanes on some approaches

• Meter entries

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‘Turbo-Roundabouts’

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The concept:

• Separate

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Mandurah roundabout – Freeway terminal

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Place ‘hook turn’ box here

The ‘hook turn’ box

provides for a cyclist

making a right turn from

the west to wait before

crossing the eastern exit to

head south. (This is what

many cyclists do at signals

– (see Austroads). In

effect, the cyclist crosses

the northern entry to the

northern bike lane entry,

then re-enters the

roundabout as if the cyclist

had arrived from the north.

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Beach Road roundabouts

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Intersections with Trams

Mt Alexander Road/Ormond Road

Toorak Road Tram Terminus

Toorak Village

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Mt Alexander Rd/Ormond Rd intersection

Observations 14 March:

• AM peak

– queues back about 200 m on northern approach

– Most others OK

• PM peak

– Generally congested – queues to east as far back as

freeway

– Queuing back from Moonee Ponds junction

– Queues to south at times to Fenton Street

– Heavy right turn south to east

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SIDRA analysis:

PM Peak Scenario SIDRA DoS Adjusted Dos

Existing conditions 0.94 0.98

+ right turn lane from south 0.69 0.65

+ right turn from south + 400 vph (S) 0.70 0.73

+ right turn from south + 400 vph (E) 0.76 0.80

+ right turn from south + 1100 vph (E) 1.04 1.09

+ right turn from south + 700 vph (s) 0.74 0.77

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Toorak Village – moveable bicycle lanes

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Lane lights

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Innovation, NZ

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