Pavement surface conditions during adverse weather WG 2

Transcription

1 Pavement surface conditions during adverse weather WG 2 Thorsten Cypra Boschung Mecatronic AG Final Conference, May 2012 Your-Name here 1

2 Research Objectives Working Group 2: Tools for road surface monitoring Analysis of weather impact on pavement under adverse weather conditions How to reduce the effect of weather? - next session 2

3 Research Objectives Example wintry road conditions: Weather Driver / Vehicle Road Conditions = relevant influence = subordinate influence Traffic Flow under Wintry Road Conditions = unchangeable or nearly unchangeable factor = limited changeable factor = changeable factor Traffic Winter Service Road Design Source: Cypra

4 Research Objectives Example wintry road conditions: Road user Road surface ABS / ESC Intelligent roads Intelligent tyres In vehicle devices Road user information Adherence Friction Salt RWIS WMMS Spreaders Road sensors Weather forecast Winter service Road / Environment Longitudinal gradient Elevation Cold spots i.e. bridges Number of lanes AADT Risk of snowdrifts US-CY Source: COST 353, Final report 4

5 Effects of weather on pavement Accident risk: Comparison of wet/dry road accidents Accident risk increases during adverse weather conditions (less visibility, reduced skid resistance,..) Drivers perceive risk only when risk is visible, for example low visibility, heavy rain, snowy road conditions - otherwise driving behaviour like wet road conditions 5

6 Effects of weather on pavement Accident risk: Rimberg Süd, Nullzustand V [km/h] q [Kfz/5min] 80 Rimberg Süd, Glätte durch Niederschlag, Schneefall > 30 Min

7 Effects of weather on pavement Tools to monitor adverse weather: Intensity of precipitation Type of precipitation Road surface condition Water film thickness on the road surface Freezing temperature Air temperature Air humidity 7

8 Effects of weather on pavement Impact of adverse weather: Differentiation between wetness and snow / ice Skid resistance: - Describes the contribution of road to tyre/road friction. - Measurement of friction under specific standardised conditions 8

9 Effects of weather on pavement Impact of adverse weather: In case of wet pavement, a film of water is created on top of the pavement that modifies the conditions. The tyre has to break the water film and to evacuate the water laterally, in order to maintain the contact between the tyre and the road surface. 9

10 Effects of weather on pavement Impact of adverse weather: Friction: - Represents grip developed by a tyre on a road surface - Longitudinal part (braking force) - Transversal part (sideway force) 10

11 Effects of weather on pavement Impact of adverse weather: Friction depends on several characteristics: - Pavement texture - Temperature - Water film thickness - Road surface condition Using skid resistance as a measurable indicator 11

12 Measuring skid resistance Skid resistance: CEN Technical Committee 227 Road Materials developed technical specifications of most commonly used skid resistance measuring devices Standardized measuring conditions: Road Temperature: +5 C to +50 C Wet surface 12

13 Country Survey on Skid Resistance Aim of Country Survey: Obtaining actual and accurate information on the devices, methods and standards for the measurement of Skid Resistance Purpose of the measurements Response from 10 countries: Belgium, Czech Republic, Finland, France, Germany, Iceland, Portugal, Spain, Switzerland and Turkey. 13

14 Country Survey on Skid Resistance Equipment use: SRT pendulum (localized measurement) Griptester (Longitudinal Friction Coefficient) SCRIM (Sideways Force Coefficient Routine Investigation Machine) (Side-force Friction Coefficient) 14

15 Country Survey on Skid Resistance Ownership of skid resistance measuring devices : Normally routine measurement equipment is owned and operated by road operators or private companies contracted by them. Special equipment is normally used by research institutes. 15

16 Country Survey on Skid Resistance Purpose of the measurements: 16

17 Skid Resistance on Wintry Roads Source: COST Action 353,

18 Skid Resistance on Wintry Roads 18

19 Skid Resistance on Wintry Roads Predicting by measuring freezing temperature actively: 19

20 Skid Resistance on Wintry Roads Measuring of friction: Non-intrusive sensors Measuring long wave infrared radiation between detector and a selected location 20

21 Skid Resistance on Wintry Roads Prediction of pavement condition: Predictions of pavement conditions based on numerical weather prediction models Different systems of Maintenance Decision Support Systems (MDSS) 21

22 MDSS in Austria MDSS situation map with risk levels:

23 Conclusion Effects of adverse weather conditions on pavement surface conditions have assessed by measuring the effect of water and snow/ice on skid resistance Wet or wintry road conditions less contact between tyre / road surface (aquaplaning) Accident risk increases - most influential factor is the driver s perception of risk 23

24 Conclusion Road authorities can perform measurements to assess road conditions and anticipate risks. Regarding water effect, measurements of rainfall intensity, water film depth on the road surface, air temperature and humidity can be useful. In winter, measurement of freezing point temperature and friction 24

25 Conclusion In countries with severe winter conditions, additional methods are in use in order to measure the actual pavement friction: Optical devices which determine the surface state and estimate the friction Friction devices, which works similar to the standardized methods On-board deceleration sensors 25

26 Conclusion Information should used in: - Traffic Management Systems - Winter Maintenance Management Systems, esp. Maintenance Decision Support Systems to increase road savety and to optimize traffic flow 26

27 Germany, December 2010 hank you for your attention! 27