1. ITS World Congress, Stockholm, Sweden Sensing the Visibility Range at Low Cost in the SAFESPOT Road Side Unit Nicolas Hautière 1, Jérémie Bossu 1, Erwan Bigorgne 1, Nicolas Hiblot 2, Adberrahmane Boubezoul 1, Benoit Lusetti 2, Didier Aubert 2 1. LEPSiS, INRETS/LCPC, Univ. Paris-Est, France 2. LIVIC, INRETS/LCPC, France

2. ITS World Congress, Stockholm, Sweden 2 Overview of the system The proposed system is a data-chain which produces environmental information in the SF Local Dynamic Map based on the detection of meteorological events (rain, fog, black ice, wet road) by one or several sensors of the SAFESPOT Road Side Unit. It refines these events, or may create a new event, by combining the outputs of the different sensors, in particular CCTV cameras. By querying the status of vehicle actuators with respect to their past locations, the component is also able to extend or reduce the detection area of this environmental event. The information is prone to be used in ‘Hazard &Incident Warning’ and ‘Speed Alert’ applications.

3. ITS World Congress, Stockholm, Sweden 3 The SAFESPOT Road Side Unit SP2SP3SP5SP4 Applications LDM API traffic event/accident, weather/road status, vehicle manoeuvres, etc GPS R/S sensing systems UDP Data Fusion Object Refinement Data Rec. Situation Refinement SP2 Framework LDM Server TCP/IP VANET Router SF vehicles Legacy systems SF vehicles Message Generation Legacy systems Gateway Responsibility Data sources ROADSIDE UNIT

4. ITS World Congress, Stockholm, Sweden 4 Map from provider Landmarks for referencing Tree Temporary regional info ! Accident Daytime Fog Congestion Ego Vehicle Ego Vehicle Road side unit Road side unit Vehicles Real time map of vehicle surroundings with static and dynamic safety information The Local Dynamic Map

5. ITS World Congress, Stockholm, Sweden 5 Road visibility Based on the French standard NF-P-99-320  The SF system shall detect visibilities below 400m  The SF system should assign the low visibilities to one of the four categories  The system should detect the origin of the visibility reduction: fog, hydrometeors Visibility rangeVisibility distance [m] 1200 to 400 2100 to 200 350 to 100 4<50

6. ITS World Congress, Stockholm, Sweden 6 Data sources: CCTV for Visibility (1/3) – Overview Technology  The sensing system aims to detect, classify critical weather conditions (dense fog, hard rain showers) and estimate the visibility range through use of classical CCTV cameras  Camera used: DALSA Genie M-1400 Resolution 1392 x 1040 with sensor 1/2" Pixels : 4.65µm* 4.65µm - 15 im/s Detection software  A background modeling approach, based on a mixture of Gaussians, is used to separate the foreground from the background.  Since fog is steady weather, the background image is used to detect and quantify it. Since rain is a dynamic phenomenon, the foreground is used to detect.  Compatible with existing video- surveillance solutions FunctionalityOperation rangeAccuracy Fog presenceDay and night100% by day Fog intensityDay>90% by day Visibility rangeDay and night>90% by day Rain presenceDay95%

7. ITS World Congress, Stockholm, Sweden 7 Data sources: CCTV for Visibility (2/3) – Fog detection Original sequence Fog detection + Meteorological visibility estimation V met Driving space area Mobilized visibility distance V mob

8. ITS World Congress, Stockholm, Sweden 8 Data sources: CCTV for Visibility (3/3) – Hydrometeors detection Original sequence Detection Segmentation Classification

9. ITS World Congress, Stockholm, Sweden 9 Situation refinement of visibility range Data fusion at RSU level:  Fog presence identified by CCTV camera  Confirmation by weather station  Combination of different sensor outputs to compute a single visibility range descriptor At road network level:  Visibility range is spatial barycenter of different sensors outputs  The corresponding uncertainty is the sum of: The uncertainty of the sensors themselves The uncertainty coming from the distance to the data sources The uncertainty coming from the status of fog lamps on the road section Possible other data sources: Mobile fog sensor Fog lamps status Visibility meter

10. ITS World Congress, Stockholm, Sweden 10 Results on LCPC test track Situation refinement of visibility range Uncertainty map Meteorological visility map  SAFESPOT camera  in-vehicle camera  Fog lights on  Fog lights off

11. ITS World Congress, Stockholm, Sweden 11 Conclusion and perspectives The performances of the detection modules are good, despite a lack of ground truth data. A more systematic evaluation should be carried out. A general framework to fuse different visibility range related data sources has been proposed. Fusion with low cost active sensors is planned. Integration and the test of ‘Hazard & Incident Warning’ and ‘Speed Alert’ applications. H&IW and SpA applications CG22 test site

12. ITS World Congress, Stockholm, Sweden 12 Annex 1: Data fusion – At the RSU level At the RSU level, fog presence is determined by the CCTV camera and may be confirmed or not by the weather station using physical constraints due to fog formation: Assuming Gaussian variables, V met and V mob are fused to obtain a single descriptor and determine the visibility range V A simple linear KF is then used to compute a weighted iterative least-squares regression:

13. ITS World Congress, Stockholm, Sweden 13 Annex 1: Data fusion – At the road network level (1/2) At a point of the road network, the visibility range depends on the surrounding data sources Each data source has its own uncertainty due to its measurement principle, e.g.: Since fog is local, the uncertainty is also strongly increasing with the distance:

14. ITS World Congress, Stockholm, Sweden 14 Corresponding uncertainty: A threshold  * is used to filter uncertain data Annex 1: Data fusion – At the road network level (2/2) The visibility distance is thus expressed by the spatial barycenter of the different sensors outputs:

15. ITS World Congress, Stockholm, Sweden 15 Annex 2: References [1] M. Jokela, M. Kutila, J. Laitinen, F. Ahlers, N. Hautière, T. Schendzielorz. “Optical Road Monitoring of the Future Smart Roads – Preliminary Results”, International Journal of Computer and Information Science and Engineering, 1(4):240-245, 2007 [2] N. Hautière, E. Bigorgne and D. Aubert, “Daytime Visibility Range Monitoring through use of a Roadside Camera”, IEEE Intelligent Vehicles Symposium (IV’08), Eindhoven, The Netherlands, June 4-6, 2008. [3] N. Hautière, E. Bigorgne, J. Bossu and D. Aubert, “Meteorological conditions processing for vision- based traffic monitoring”, IEEE International Workshop on Visual Surveillance (VS2008), in conjunction with ECCV, Marseille, France, October 2008. [4] N. Hautière, J. Bossu, E. Bigorgne, A. Boubezoul, N. Hiblot, B. Lusetti, D. Aubert. “Sensing the visibility range at low cost in the SAFESPOT Road Side Unit”. Accepted in ITS World Congress (ITS’09), Stockholm, Sweden, September 2009. [5] N. Hautière, A. Boubezoul, Extensive Monitoring of Visibility Range through Roadside and In- Vehicle Sensors Combination, submitted to IEEE International Conference on Advanced Video and Signal-based Surveillance (AVSS’09), Genoa, Italy, October 2009 [6] J. Bossu, N. Hautière, J.-P. Tarel. Utilisation d’un modèle probabiliste d’orientation de segments pour détecter des hydrométéores dans des séquences vidéo, XXIIème colloque GRETSI (GRETSI’09), Dijon, France, Septembre 2009