1. Impacts of Reducing Freeway Shockwaves on Fuel Consumption and Emissions Meng Wang, Winnie Daamen, Serge Hoogendoorn, Bart van Arem Department of Transport&Planning
February 24, 2019

2. Outline Introduction Approach Application&Results Conclusions
February 24, 2019
Meng Wang
Department of Transport & Planning

3. Background Increasing congestion Freeway control measures in freeways
i.e. SPECIALIST (SPEed ControllIng ALgorIthm using Shockwave Theory)
February 24, 2019
Meng Wang
Department of Transport & Planning

4. Background2 Increasing public concerns on environment and health
Both sustainability and throughput should be considered when implementing control measures
Question need to be answered:
What are the impacts of freeway control measures (i.e. SPECIALIST) on fuel consumption and emissions?
February 24, 2019
Meng Wang
Department of Transport & Planning

5. Problem statement Macroscopic emission models
Average trip speed as inputs
Estimating emissions for large scale network, i.e. a country or a city
Microscopic emission models
Microscopic traffic data (speed and acceleration) as inputs
Appropriate for estimating emissions at link level
We have loop detector data
Lack of microscopic traffic data
We have loop detector data
Possibility to extract microscopic information from them
February 24, 2019
Meng Wang
Department of Transport & Planning

6. Approach Speed map at equidistant output grid of 100m*10s
February 24, 2019
Meng Wang
Department of Transport & Planning

7. Approach-Acceleration estimation
Assuming vehicle n enters a grid (i, j) with position and time (xentry,tentry), and travels with a speed as a linear function of speed
at spatial cell boundaries
Trajectory can be obtained by solving the equation
with x(tentry)=xentry
Acceleration can be estimated
February 24, 2019
Meng Wang
Department of Transport & Planning

8. Application Assessing the environmental impacts of SPECIALIST
A freeway control algorithm dedicated at reducing shockwaves on Dutch freeway
Detects traffic states and predicts their future evolution using Shockwave theory
Resolves shockwaves by implementing dynamic speed limits at different locations
Field implementation since September 2009
On A12 going from the connection with the N11 at Bodegraven up to Harmelen.
February 24, 2019

9. Application- data set
Double loop detectors with typical distance of 300 to 600m
Time period is morning peaks from 6.00 to hours.
Weekday data from January to May in 2006 as Before-SPECIALIST situation.
Weekday data from September to December in 2009 as After-SPECIALIST situation.
Unusual congested days are excluded from the dataset.
February 24, 2019
Meng Wang
Department of Transport & Planning

10. Results Indicators Before After Change Average Flow (veh/h) 4761 4991
4.83%
Average Speed (km/h)
91.24
91.75
0.56%
Average acceleration (m/s2)
0.023
0.022
-4.35%
Standard deviation of acceleration (m/s2)
0.0828
0.0631
-23.79%
Average Fuel consumption
(veh/100 km)
9.0266
8.9852
-0.46%
Average NOx emission (mg/s)
7.7306
8.1590
5.54%
Total Fuel Consumption (l)
1.0820e+04
1.1178e+04
3.31%
Total NOx emission (g)
3.5092e+04
3.6682e+04
4.53%
February 24, 2019

11. Fuel rate Average speed NOx rate
The average fuel consumption rate per vehicle decreased slightly. Clear benefits of average fuel consumption rate in congestion area from 8 to 9 am.
Average NOx emission rate per vehicle increased by 5.54% after implementing SPECIALIST.
Increase in total fuel consumption and emissions After-SPECIALIST.
It is difficult to conclude whether implementing SPECIALIST can reduce total fuel consumptions and emissions in the considered road stretch, for the benefits might be compensated by the increase of demand in the network.
February 24, 2019
Meng Wang
Department of Transport & Planning

12. Conclusions
The proposed approach provides a way to estimate fuel consumption and emissions based on macroscopic traffic data
Potential application includes assessing the impacts of traffic control measures on sustainability at link level
Certain dynamic traffic management measures may have different impacts on different indicators of fuel consumption and emissions.
Suggestion:
Dynamic traffic management measures should be carefully designed if they are aimed at reducing fuel consumption and emission.
February 24, 2019
Meng Wang
Department of Transport & Planning

13. Thanks! Comments & Questions? February 24, 2019 Meng Wang
Department of Transport & Planning

14. Fuel consumption with speed&acceleration NOx with speed&acceleration
February 24, 2019
Meng Wang
Department of Transport & Planning

15. Detector spacing=500m Detector spacing=1000m February 24, 2019
Meng Wang
Department of Transport & Planning