Socioeconomic effects of optimised traffic signals

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Socio-economic effects of optimised traffic
signals
Samfundsøkonomiske effekter af bedre
trafiksignaler

• Steen Lauritzen
• Vejdirektoratet (DK)

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Content

• Costs of stops and delays at red lights
• The importance of keeping traffic signals at a
  high level of quality
• Signal projects in the Road Directorate
• Effects of improvement of signal timings
• Conclusions

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Important issue in the press
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Traffic signals and the society

• Traffic signals are a crucial component of a
  citys network
• We cant live without them

• Negative impacts
• Delays
• Stops
• Emissions, pollution
• We must keep their negative impacts as low as
  possible

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Yearly costs (low estimate)

• 2700 traffic signals in Denmark
• Estimated yearly costs 7,4 mrd DKK
• Delays 4,4 mrd DKK
• Stops (6,6 mrd/år) 1,1 mrd DKK
• Accidents 1,9 mrd DKK
• Fuel consumption (0,6 mrd DKK ex. tax)

• Per traffic signal 2,7 mill. DKK
• Sverige, 1995 4,2 mill. SEK

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Ageing of signal timings
Ageing 2 4 per year
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Why improve traffic signals ?

• Reduced travel time
• Fewer stops
• Reduced congestion
• Less driver frustration
• Reduced fuel consumption
• Less wear and tear on vehicles
• Less pollution
• Less CO2-emission

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Facts about traffic and signals

• 40 of fuel consumption in a signalised network
  burned at traffic signals, stop, idle, go
  (TRANSYT)
• 30 of all vehicle-km travelled in signalised
  networks (California)

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Two projects in 2007

• Analysis of total costs in traffic signals and
  potential for improvements
• Strategy for operation of the Road Directorates
  400 traffic signals

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Litterature study

• Approx. 70 reports and articles mainly from
  Scand., Europe and USA

• Potentials for reductions
• Co-ordinated, fixed-timed 5-20 in delay
• Adaptive 5-15 in delay
• Fuel consumption 5-10
• Highest pay-back rate in cheap projects !
• Maintaining detector equipment is crucial
• Recommended traffic engineering inspections every
  3 to 5 years

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(No Transcript)
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FETSIM (USA)
Fuel Efficient Traffic Management Federal support
to retime 12 000 traffic signals from 1983-93
(16 mill. )

• Fuel savings/cost ratio 51 (500)
• Total benefits/costs ratio 511 (5000)

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13 TRANSYT-projects in DK
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Signalised diamond
Morning peak signal timings
Before
After
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Signalised diamond
Delay in morning peak hour, before and after,
calculated by simulation (VISSIM)
Benefits Per hour 7 700 DKK Per year
3,1 mill. DKK Investment 0,1 mill. DKK Pay
back time lt 2 weeks
less fuel consumption 170 litres/hour
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Effects of detector failure

• 4-way junction with AADT12000 veh.
• Fully vehicle-actuated
• Rest-in-red
• Speed-limit 60/50 km/h
• Effects simulated for a 24-hour period in
  VISSIM

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Results for a weekday
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First year benefit
1000 kr
Huge benefits at almost no costs !
3000
2500
2000
1500
1250
1000
500
500
120
25
12
250
0
Reparere en
Optimering af
Nyt
1 meter
1 meter
detektor
signalanlæg
styreapparat
Øresundsbro
Motorring 3
smarte
funktioner
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Number of stops can be reduced
Saturday afternoon, 2006
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Conclusions

• Old wine in old bottles
• Large potential for better traffic signals
• CO2 reductions may be an argument
• Maintaining detectors is crucial for traffic flow
  (and safety)

• We know what to do, and how to do it !

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Questions?