a new tool to evaluate safety of crossroad

A NEW TOOL TO EVALUATE SAFETY OF

CROSSROAD

Peggy SUBIRATS (corresponding author)

Centre d’Études Techniques de l’Équipement Normandie Centre – ERA 34 10 chemin de la Poudrière, BP 245, 76121 Le Grand Quevilly Cedex Email : [email protected] Phone : +33 (2) 35 68 81 79 Yohan DUPUIS

IRSEEM Technopôle du Madrillet, Avenue Galilée BP 10024, 76801 Saint Etienne du Rouvray Cedex Email : [email protected] Phone : +33 (2) 32 91 58 14 Eric VIOLETTE

Centre d’Études Techniques de l’Équipement Normandie Centre - ERA 34 10 chemin de la Poudrière, BP 245, 76121 Le Grand Quevilly Cedex Email : [email protected] Phone : +33 (2) 35 68 81 33 David DOUCET

Centre d’Études Techniques de l’Équipement Normandie Centre – ERA 34 10 chemin de la Poudrière, BP 245, 76121 Le Grand Quevilly Cedex Email : [email protected] Phone : +33 (2) 35 68 81 34 Guy DUPRE

Centre d’Études Techniques de l’Équipement Normandie Centre – ERA 34 10 chemin de la Poudrière, BP 245, 76121 Le Grand Quevilly Cedex Email : [email protected] Phone : +33 (2) 35 68 81 30

ABSTRACT

In this paper, we present a tool to evaluate the safety of crossroads. To accomplish this task, the proposed system detects and registers the near miss accidents. The final goal is to assess the impact of improvement on existing road designs and crossroads facilities. This tool uses traffic analyzer like speed radars and pneumatic tubes to detect vehicles on the main road and its branches. Data coming from the radars and the road tubes are transmitted through the wireless networks to a processing unit. Then, an algorithm calculates the time to collision to detect near miss accidents. Finally, the uniqueness of the proposed solution lies in a video recorder which continuously records and preserves thirty seconds before and fifteen seconds after the incident. This allows us having a qualitative analysis, a complete mathematical formulation and easily determining if the near miss accidents result from a driver error or a road design problem. This system isn't bulky and can be easily set up on different kinds of crossroads. In fact, a very short time (nearly one hour) is required to install all its components.

Subirats, Dupuis, Violette, Doucet and Dupre 3

INTRODUCTION

Rural roads are more dangerous than other roads. In Europe, more than 80% of all fatal collisions occur on rural roads. Rural roads account for 60% of road fatalities (1, 2) compared to 10% for motorways (1, 3). Three accident types are reported under car collisions on rural roads: single-vehicle accidents (e.g., run-off-road with further collisions with dividers and utility poles); head-on collisions; and collisions at intersections. On the rural roads, one accident out of 10 occurs at intersections. Their severity is 5.3 times higher than in urban areas.

Facing this reality, we decided to develop a tool to evaluate the safety level of a crossroad. The objective is to give an indicator of intersection dangerousness. This safety indicator is defined at the end of this paper. Here, we first present the context and the needs that motivated the development of this system. In the second part, we detail the system specifications. Its set up on the intersection is presented in the third part. In the forth part, we define a safety indicator in a crossroad. In a last part, we show some results and finally, we conclude and give some perspectives of this work. 1. CONTEXT AND NEED ANALYSIS

The present study is a part of the French national multidisciplinary research project PREDIT-SARI. This national project aims at informing drivers and road managers more effectively, about the high risk of loosing control on the rural road network. In this context, we have developed a system to fulfil the criteria and the needs mentioned above. 1.1 A strong challenge

In France, intersections represent less than 1% of the distance traveled by users, but over 10% of accidents. The risk of an accidents, for a user traveling on a rural road, is multiplied by 10 at an intersection. 1.2 A road manager’ s need

The danger posed by intersections, results in a strong social pressure to secure these sites. The user facility requires a safety diagnosis whose goal is to understand accidents process. However, at intersections, there are only few injury accidents, and often the police report is incomplete. Indeed, the hearing of the user driving on the secondary road is not completely take into account because of the lesser degree of seriousness of his injuries. Consequently, road managers have a lack of data to understand the problems of the site.


Road managers want to quickly measure the effectiveness of a modified facility, improvement of facilities or environmental modification. On this type of site, accident analysis requires a decline of 3 to 5 years to determine the effectiveness of a change. This delay doesn’t correspond to the expectations of managers, or those of users. To provide a high level security, managers are implementing many innovative developments such as: crossroads chicane wall effect, dynamic warning signs, rural roundabout and so on. Managers need to quickly evaluate these innovations. 1.3 Definition of a crossing at grade near-miss and system goals The system described hereafter intends to understand disorders in a crossroad and to evaluate the effectiveness of facilities. It detects and records conflicts between users on the non-priority road who cross the road in front of the users driving on the priority road in straight motion. This type of conflict represents the main type of accidents called crossing at grade accidents. A precise study of the patterns encountered at accident-prone intersections on the rural roads, showed that some situations are much more dangerous and more common than the others. In particular, cross movements at the main road cause most of the accidents at the intersections. These movements are called “1st and 2nd crossing at grade”. A crossing at grade occurs when a vehicle situated on the minor road enters into the intersection and a vehicle driving on the main road crashes it. This is called a 1st crossing at grade when the vehicle driving on the main road comes from the left with respect to the vehicle situated on the minor road (Fig 1.a). This is called a 2nd crossing at grade when the vehicle driving on the main road comes from the right with respect to the vehicle situated on the minor road (Fig 1.b).

(a) (b)

FIGURE 1 Illustration of crossing at grade accident: (a) a 1st crossing at grade, (b) a 2nd

crossing at

grade accident

So, to meet the diagnosis and assessment needs, we thought to detect and record near-miss accidents (and not accidents) related to the movement of 1st and 2nd crossing at grade. This min goal is to give to the road managers an idea of the safety level of the intersection without waiting for many accidents to occur. Thus, the system detects situations that are similar to the concept of traffic conflict defined by Amunndson in 1977. A traffic conflict (also called near-miss accident) is "an observable situation, during which two drivers approach one another in time and space, to a point where there is a risk of accident if their movements remain unchanged " (11,12,13). Thus, our system detects situations as mentioned above in (11).


2. THE NEAR-MISS ACCIDENT DETECTION SYSTEM SPECIFICATIONS

In this part, we present the specifications chosen for developing our system. 2.1 Principle

The proposed system principle is shown in the figure 2.

FIGURE 2 Principle of the near miss accident detection system

Once a non-priority vehicle, i.e, a vehicle coming from the minor road, starts and gets into the intersection, two confidence intervals are defined (1st junction confidence interval and 2nd junction confidence interval). If a vehicle driving on the main road is detected during these intervals, we face a near-miss accident. Both confidence intervals are empirically defined depending on the kind of intersection. These parameters can easily be changed prior to the system installation. The time to collision (TTC) between a vehicle getting into the intersection from the minor road and a vehicle driving on the primary road is defined as the difference in the time between the moment when the non-priority vehicle restarts from the stop line and the moment when a vehicle is detected on the main road. The time to collision measurement between a minor road driver and a primary road driver is possibly a representative of an intersection security level. Furthermore, the addition of a video system in the analysis allows better understanding of why these situations occurred. By analyzing the videos, we have the possibility to checking if they result from a driver error or an intersection design problem. 2.2 Technical specifications

In order to be operational and easy to use, the developed system has to satisfy the following requirements:

o Detection of vehicle entering the intersection from the minor road,


o Detection of straight moving vehicles and discard turning vehicle from the major road,

o Calculation of the time to collision, o The system has to be installed onto different kinds of intersections, o The system must use wireless technologies, o Rapid installation of the system on the intersection without disrupting the traffic, o The system must work with an autonomous energy like solar energy or windmill.

Measurement taken for one week are enough to have an idea of the intersection safety, o The system must satisfy the regulations concerning the safety of the users and

roadside obstacles, o The system should ensure the security against theft (atmospheric condition, etc).

3. THE NEAR-MISS ACCIDENT DETECTION SYSTEM PRESENTATION

3.1 The system developed

The principle of the system is presented in figure 3.

FIGURE 3 Near-miss accident detection system diagram

First, the system detects vehicle driving on the main roads. Out of many existing traffic sensors, we chose to use speeds radar. The speed parameter allows to distinguish between vehicles going straight with the vehicles having a turning movement that can’t be involved in a near-miss accident. As we can’t possibly use wired solution, we propose a WIFI transmission. For this, speed radars send the data measured via a WIFI transmitter to an access point connected to the central system. Then, the system detects vehicles situated on the minor road and entering the intersection. For this, we use a pneumatic tube placed on the stop line. This technology is enough to detect vehicle and is easy to install. The information about the presence of a non-priority vehicle on the minor road is sent via a radio transmitter to a radio receiver which is connected to the central system. The central system consists of an industrial computer that calculates the time to collision. If this time is less than 5 seconds (or 7 seconds), we are confronted with a 1st line near-miss accident ( 2nd line near-miss accident respectively). The scene is continuously recorded and maintains constant buffer of 30 seconds which can be retrieved when required. Once a near-

Priority vehicle detection

Non-priority vehicle detection

Industrial

computer

(Near-miss accident

detection)

Video recording

WIFI transmission

Radio transmission


miss accident is detected, a video system records the video of 30 seconds before and 15 seconds after the near-miss accident. The video allows to understand what happens and if the road infrastructure or the driver behavior is responsible for the situation. 3.2. Results

Our system was evaluated on a rural road located in the city of Gouy (Normandy, France). The intersection is illustrated in the figure 4.

FIGURE 4 Example of instrumented intersection

The instrumentation is illustrated in figure 5. On the right down, a box containing radar and WIFI transmitter is situated on the shoulder. On the right up, a pneumatic tube situated on the stop line and a box containing the radio emitter.

(a) (b)

FIGURE 5 Near-miss accident detection system illustration. (a) the control unit associated with a

registration system. (b up) the system for detecting non-priority vehicles. (b down) the case containing the

system used to detect vehicles on the major road.


The system stores all vehicle speeds, restarting of non-priority vehicles and near-miss accident video. An example of near-miss accident recorded by our system is given in figure 6. The non-priority vehicle has restarted from the minor road in order to enter the intersection before a tractor (as we can see in Fig. 6.b). Yet, the vehicle driving on the main road had to apply brake to avoid the collision.

(a) (b) (c)

FIGURE 6 Example of near-miss accident detected with our system

4. DEFINTION OF A RISK INDICATOR

In this part, we propose the definition of a crossroad risk indicator. The proposed indicator is defined below:

( )r i i

i

I G C=∑

Where Ir is the risk indicator, Gi is the conflict number i and Gi(Ci) is the gravity of the conflict i. So,the proposed indicator is equal to the number of conflicts (near-misses), weighted by the severity of the conflict recorded in a given period (15). We chose to take the number of conflicts per hour. The weight of a conflict is defined as followed: the severity of a conflict depends on vehicle speed and time to collision.

G = T

KS12

T = time to collision between both vehicles at the conflict point

S = priority user speed.

K = constant number


CONCLUSION

In this paper, we have presented a tool to the evaluate safety of crossroads. This tool can easily be installed on different kinds of intersections. The developed system detects and records near-miss accidents. In perspectives of this work, the system has to be tested on several intersections in order to validate our empirically defined risk indicator. Finally, on the long run, our system will be helpful for road managers to complete security diagnosis.

ACKNOWLEDGEMENTS

The research presented in this paper was performed as part of the French National project PREDIT-SARI, sub-them RADARR sponsored by the National Research Agency.


REFERENCES

(1) IRTAD (International Traffic Safety Data and Analysis Group). Fatalities by Road

Location, 2007. www.cemt.org/irtad/IRTADPUBLIC/we32.html. Acceded Jul. 1, 2008. (2) ONSIR. Observatoire Nationale de la Sécurité routière, 2008.

www.securiteroutiere.equipement.gouv.fr/infos-ref/observatoire:Synthese.html Acceded Jan. 16, 2008.

(3) SafetyNet. Annual Statistical Report 2006, 2007. (SafetyNet: EC-Contact no.: TREN-04-FP6TRSI2.395465/506723, Project Number: 1.3.2). www.erso.eu/safetynet/fixed/WP1/2006/SN 1 3 ASR 2006 final.pdf. Acceded Mar. 14,

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INRETS n° 11. (10) Picado- Santos. Rodrigues. (1998), « The Application of Traffic Conflict techniques in

validation of low cost safety Improvement Measures ». (11) Amundson, F. et Hyden, « C. Proceeding (1977)First workshop on traffic conflits. Institute of Transport Economics Oslo Norway. (12) Glauz, W et Migletz D. (1980), « Application of traffic conflits analysis at intersections ». NCHRP report 219. Transport Research Board. Whashington DC (13) Muhlrad N (1993), « Traffic conflict techniques and other forms of behaviour analysis:

Application to safety diagnoses ». 6 th ICTCT Workshop. Salzburg (14) T Brenac . (1992), « Sécurité des Routes et des Rues » SETRA CETUR (15) T Brenac (1994), « Accidents en carrefour sur routes nationales. Modélisation du nombre d’accidents prédictible sur un carrefour et exemples d’applications ». INRETS rapport 185 (16) CETE NC SETRA (2001), « Typologies des accidents en intersections sur routes interurbaines ».

a new tool to evaluate safety of crossroad

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