thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

Road Information Sharing Using Probe Vehicle Data in Disasters
1234Y. Hada , N. Kodama , T. Suzuki and K. Meguro1

Research Fellow, Institute of Industrial Science, The University of Tokyo, Japan
Assistant Professor, Waseda Institute for Advanced Study, Waseda University, Japan
3Professor, Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, Japan
4Professor, Institute of Industrial Science, The University of Tokyo, Japan
Email: haday@iis.u-tokyo.ac.jp
2ABSTRACT :Road information sharing is vital in disaster response, but it still remains today a significant problem in spite of
the recent breakthrough of information and communication technology.
In this study, we overview the present situation and structure problems on road information sharing. Two main
problems are as follows: i) how to gather the information about which road can be used and ii) how to share theinformation among different disaster information systems used in the authorities concerned.
We propose road information sharing using probe vehicle data to solve the first problem. The characteristics andthe possible use of the GIS plotted probe vehicle data in past disasters are discussed. The probe vehicle data
provide information to decide which road are likely to remain available at the time, and also where the vehicle
turned around, that indicates the road might not be available.
The travel time of individual car trips are numerically simulated with and without road information sharing
among the cars. The reductions of the travel time depend on numbers of probe cars and road closures. The
simulation results indicate that the probe vehicle data can be effectively used to reduce the travel time in a timeof disaster, and to gather regional information on available roads.
KEYWORDS:
Probe vehicle, Road information, Information sharing, Disaster response
1. INTRODUCTION
Sharing traffic and road information is essential for effective disaster response. Despite the remarkable progress
made recently in the fields of information and communication technology, there is currently no generally
accepted solution for this problem.
Here, we examine the current status and problems faced in sharing traffic and road closure information. We also
propose and evaluate a new method for sharing information about road closures using probe vehicle data. Theprobe vehicles have been practically employed in the transportation field as a means of gathering informationsuch as speed and direction from cars that are currently available
2. CURRENT STATUS OF INFORMATION SHARING DURING DISASTERS
In this chapter, we present an overview of the schemes currently used for sharing road information andinformation content. Most of the existing schemes are limited to major roads.
The Ministry of Land, Infrastructure and Transport (MLIT), Government of Japan, monitors the damage andavailability of roads. Fig. 1 shows a system for road information collection on road administrators in Japan.
Road information grasped each road administrators is reported to higher organizations in the way shown in Fig.
1, finally is collected by the head office of MLIT. In large scale disasters it takes much time on road informationcollections. Based on the interview investigation about road information collection in the 2004 Mid Niigata
Prefecture Earthquake to National Highway and Risk Management Division of MLIT, collected all roadregulation information (more than 200 regulations executed) is drawn on to a map 3 days later the occurrence ofthThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, ChinaExpresswaycompaniesExpressways
Toll roads administrated
by expressway companies
National highways
administrated by MLIT

National highwayoffices

National highways administrated
by prefectural governments

Prefecturalgovernments

Regional DevelopmentBureaus

The head officeof MLIT

Nationally administrated
roads
Toll roads administrated
by public sectors

Fig. 1

Public corporations

System for road information collection on road administrators

the earthquake. During disasters, road information is provided through the Internet and electric bulletin boards
installed above the roads. The tabular information provided on their web site includes road closures and traffic
control information of major roads.
The Japan Road Traffic Information Center (JARTIC) provides information gathering and distribution servicesdelegated by traffic administrators and road authorities such as the National Police Agency and MLIT. Traffic
and road information is widely distributed through radio, television, and the Internet. The tabular graphicaltraffic information provided on the JARTIC web site includes the route name, section and direction, cause oftraffic, and details regarding traffic control.
The Vehicle Information and Communication System (VICS) transmits literal graphical traffic information tothe in-car navigation system. Drivers can acquire real-time traffic information, as well as other information suchas vehicle speed, travelling time, accidents, roadwork, speed limits, lane closures, and car parks. Approximately
70,000 km out of a total road length of 330,000 km of major roads are covered.
3. PROBLEMS FACED IN SHARING TRAFFIC AND ROAD CLOSURE INFORMATIONRoad information about both the disaster site and its surrounding areas is required for interregional rescues andbackups during disasters. This implies that several road administrators are expected to share their roadinformation. We structure the problems faced in road information sharing during disasters to road users andadministrators through interview analysis.
3.1. Lifeline suppliers and physical distribution companies(i) It is difficult to locate the exact position from literal road or traffic information.
(ii) A lack of information about road availability and damage severity was experienced.
(iii) Road information could not be obtained in a timely manner while driving in the areas affected by thedisaster.
(iv) No special road information is provided to emergency vehicles, although they are given priority.
(v) Reliability, update frequency, and last update time of information were not available.
(vi) Sharing of road information and coordinated sources of information are required.
3.2. Road administrators(i) Traffic regulation sections cannot be exactly located because their names are not standardized.
(ii) Regional road information that is required for finding a diversion is not shared.
(iii) An integrated road information service is not available during disasters.
(iv) The total length of the local roads is so long that it cannot be supervised by an administrator in a short timethThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, Chinaspan.
(v) An information system is required to gather road information from local residents and drivers, and to shareand provide it.
3.3. Police departments(i) Traffic control information is gathered through facsimiles and e-mails whose structures are not standardized.
Subsequently, the traffic control sections are drawn onto a paper map.
(ii) High priorities are given to rescue operations, followed by disaster prevention and evacuation guidance;road information is vital in such situations.
Based on these interview results, the road information sharing problems are structured in a cause-and-effectdiagram (Ishikawa, 1986), as shown in Fig. 2. The important points that must be considered for effectively
sharing road information are as follows: (1) rapid checks for road availability and (2) providing prompt accessto road information. The sharing of probe vehicle data, which is explained in the following section, is proposedin order to solve the first problem described above.

Lifeline suppliers and physical distribution companies
Unknown update frequency of road information

Road information is located slowly

Unknown reliability of road information

Literal traffic
regulation information

Non-standardized names oftraffic regulation sections

No special road informationfor vehicles given priority

Traffic regulation information
is drawn slowly onto a map

No information on available roads
No information on damage severity

Road condition changes with time
Integrated road information
service not available

Road information published through own platform
Difficult to integrate information intoa system

Roads damaged simultaneously

Slow to grasp
available roads
Communication by police radios

Limited information exchange

Information from drivers not used

Difficult to input andbrowse information

Limited information disclosure
for security reasons

Slow to grasp road damage

Limited access to internet
for security reasons

Unmanaged road facilities
No origin for positioning specified

Traffic is not thetop priorities

Road condition changes with time

Local roads have long total length

Administrators become victims
Communication blackout
Roads damaged simultaneously
Reporting through facsimile and e-mailLocal roads are checked slowly
Rescue and evacuation are
the highest priority

GIS is not common

Many administrators fordifferent road types

Difficult to share information

Poor information sharing
among administrators
Police departments

Fig. 2

Non-standardized road information
Difficult to share information among systems

Road administrators

Cause-and-effect diagram of road information sharing problems

thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
4. EXAMPLE OF PROBE VEHICLE DATA IN DISASTERS
Fig. 3 shows the positions of probe vehicles every six hours after the occurrence of the 2004 Mid Niigata
Prefecture Earthquake until the end of the next day. The short red lines indicate road closures that were enforced
during that period. The trajectory records of some vehicles indicate that they were within the road closure
sections; this occurred because these vehicles travelled in these sections before they were closed, or the literal
information interpreted the length of the road closure to be longer than its actual length on the map. Since thenumber of probe vehicles was not enough, most of roads are not travelled by probe vehicles. Suppose that theMotorway
National road
Major street
Prefectural road
Other roads
Road closure
18–24, 23rd Oct.
0–6, 24th Oct.
6–12, 24th Oct.
12–18, 24th Oct.
18–24, 24th Oct.

Fig. 3 Probe vehicle trajectories after the 2004 Mid Niigata Prefecture Earthquake

05:32:35

05:32:19

05:30:1905:27:19

Fig. 4 Trajectory of a car turned around before road closuresthThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
number of probe vehicles is much enough to cover all roads and probe vehicles information can be gathered inreal-time. Trajectories of probe vehicles can be utilized for judgments which road is available. For all peoples
such as rescue crews travelling to the suffered area, this information contributes better judgments on theselection of the route to the destination in an emergency phase of lack of road information.
Fig. 4 shows the trajectory of a vehicle that turned around before the road closures. If the cause of a car turned
can be discriminated road closures from the others such as just stopping by a convenience store on the opposite
direction, road closure points can be detected automatically.
5. PRELIMINARY NUMERICAL SIMULATION
It is vital for prompt and effective disaster response to gather information on available roads as well as roadclosures. In this chapter, the information gathered on available roads by combining the trajectories of probevehicles is numerically simulated. The travel time saved by sharing the road closure information is also
discussed.
5.1. Outline of numerical simulation
In the simulation, probe cars travel in a road network of the Niigata Chuetsu region, as shown in Fig. 5. Thenetwork includes approximately 7,500 links and its total length is around 4,240 km. The black links indicate
road closures approximately thirty hours after the occurrence of the 2004 Mid Niigata Prefecture Earthquake.
Each vehicle is equipped with a car navigation system that processes the probe data. The vehicles move on theshortest paths to their destinations and avoid using closed links. All vehicles gather road closure information(link ID) during transit and shared this information among each other. It is assumed that the road closure
information is obtained from the trajectory analysis of the probe vehicles or through direct data input to the carnavigation device by the drivers.
Here, we compare the travel times and rates of the known available roads with and without road closure
information sharing. The rate of known available roads Rk is defined as follows:

Closed linkFig. 5Road network of Niigata Chuetsu region

thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, Chinal
Rk ＝ ∑ i(5.1)∑ Li

whereli :Li :Length of available link that was used by at least one vehicle
Length of available link

At the beginning of the simulation, every vehicle searches for the shortest path to its destination without the useof road closure information, and then it begins travelling. The vehicles share the road closure information while
they travel according to the following rules.
(i) Vehicles simultaneously share road closure information obtained during driving every 5 min via the dataserver, and search for a new shortest path. If a vehicle encounters a road closure, the closure is added to thatvehicle’s database, and a new shortest path is searched.
(ii) When vehicles encounter a closure, they upload the road closure information gathered during driving anddownload the known road closure information uploaded by other vehicles. Subsequently, the shortest paths
are updated.
(iii) Road closure information is not shared. If a vehicle encounters a road closure, it is added to that vehicle’s
database, and a new shortest path is searched.
In rules (i) and (ii), the information sharing frequencies are selected so as to avoid excessive communication
cost.
Here, we do not consider heavy traffic in order to discuss the primary effect of information sharing on roadinformation gathering and reducing the travel time. The road closures are not supposed to change during theentire simulation time, and consequently the probe vehicle data once gathered is valid until a simulation comesto an end. If an ever-changing road condition is assumed, only the latest probe vehicle data should be used inorder to calculate the shortest path to the destination.
Vehicles drive a linear distance of 50 km at an average speed of 30 km/h. The journeys of 20, 50, and 100
vehicles are simulated. A hundred pairs of origins and destinations are randomly selected, and the travel times
and rates of known available roads Rk are calculated.
5.2. Results of numerical simulation
5.2.1. Available road information gathering

Closed link
Trajectory of vehicle(a) Road information shared every 5 min

Fig. 6(b) Road information shared on
encountering closures(c) No road information shared

Examples of simulated trajectories (100 vehicles)thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

Information shared every 5 min
Information shared on encountering a closure
No information shared
No road closure
0.5Rk

0.4

100 vehicles

0.3

50 vehicles

0.2

20 vehicles

0.1
00Fig. 7

200

400
600
800
Time (min)Time histories of average rate of known available road RkOD

Travel time: 198 min(a) Road information sharedevery 5 min

Fig. 8OODD

Travel time: 207 min

Travel time: 557min(b) Road information shared onencountering closures(c) No road information
sharedExamples of simulated trajectories (One vehicle selected from Fig. 5)

As an example of the simulation results, the trajectories of 100 vehicles are shown in Fig. 6. The layout of theavailable roads can be instantly recognized. These figures show the results of the three information sharing
schemes mentioned in 5.1; however, there is no significant difference among them. In Fig. 6, the same
phenomena is shown in time histories of Rk, which implies that the information sharing schemes have nosignificant influence on Rk saturation values of 0.2, 0.3, and 0.4 for 20, 50, and 100 vehicles, respectively. The
results without road closure are also shown for comparison in Fig. 7. Rk saturates with time because the numberof vehicles that have arrived at destinations increases and fewer vehicles contribute to the increase in Rk. Further,Rk saturates earlier as the number of total vehicles increases because of an increase in the possibility of othervehicles discovering the road closures on the shortest path of one vehicle.
5.2.2. Travel time reduction
Fig. 8 shows the trajectories of one vehicle selected from among those of the hundred vehicles shown in Fig. 5.
The trajectories with and without road closure information sharing are found to be remarkably different. In thisexample, a travel time of 557 min when road closure information is not shared is reduced to 198 min when it isthAverage travel time (min)The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

No information shared
Information shared
30020010002050100
Num. of probe vehicles participated information sharing

Average travel time (min)(a) Road information shared every 5 min
No information shared
Information shared
30020010002050100
Num. of probe vehicles participated information sharing(b) Road information shared on encountering closures

Fig. 9Reduction of average travel time by road closure information sharing

shared every 5 min, and to 207 min when it is shared on encountering road closures.
The average travel time is also reduced, as shown in Fig. 9. This figure shows that an average travel time of 330
min when road closure information is not shared is reduced by the sharing of road closure information sharing.
The reduction becomes more significant as the number of vehicles increase, and in the case of 100 vehicles, theaverage travel time reduces by 30%. The difference between the information sharing schemes has no significant
influence on the rate of reduction in average travel times.
6. CONCLUSION
We overviewed the problems encountered in sharing traffic and road information during disasters from theviewpoint of an interview investigation, and structured these problems in a cause-and-effect diagram.
The important points to effectively share road information are as follows: (1) rapid checks for road availabilityand (2) providing prompt access to road information. We proposed probe vehicle data sharing to resolve the firstproblem. The actual probe vehicle data in a disaster was introduced and its effectiveness in disaster response
was presented.
Vehicle trajectories on a real road network with road closures were numerically simulated. In the simulations,heavy traffic is not considered because its effect on road information gathering and reduction in travel time iscoupled with that of information sharing.
The available roads were readily recognizable when the trajectories obtained from the vehicles weresuperimposed on a map. The simulated travel times of individual vehicle journeys were shortened when the roadthThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China
closure information derived from the probe vehicle data was shared among the vehicles. The sharing of roadclosure information marginally affects the total length of the available roads that is recognized.
The simulation results indicate that the sharing of probe vehicle data can allow for information on available
roads in a wide area to be gathered rapidly, and effectively reduce travel times of vehicles being driven in adisaster site, including the travel time of the disaster response authorities.
Vehicle trajectories do not ensure that the roads travelled by the vehicles are safe, and therefore the trajectory
information should be shared with an understanding of its characteristics. Appropriate use of this information
can enable prompt and effective disaster response.
7. ACKNOWLEDGMENTS
We are thankful to Prof. Masao Kuwahara, the University of Tokyo, for providing advice and suggestions. We
also extend special thanks to Honda Motor Co., Ltd. for providing us with probe vehicle data.
This study was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT),
Japan.
REFERENCES
Ishikawa K.(1986), “Guide to Quality Control”, 2nd Revised Edition, Asian Productivity Organization
Japan Road Traffic Information Center web site (http://www.jartic.or.jp/, in Japanese).
Road Bureau, The Ministry of Land, Infrastructure and Transport, "Monitoring of traffic congestion deployment of probe cars -", ITS Handbook Japan 2002-2003(http://www.its.go.jp/ITS/2002HBook/section4/4-9e.html).
Vehicle Information and Communication System Center web site (http://www.vics.or.jp/english/).