Paper ETCTag

8/6/2019 Paper ETCTag

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TRAVEL TIME REGISTRATION USING ETC TAGS INNORWAY

Mr Torbjrn Haugen

Research ScientistSINTEF

NO-7465 Trondheim, NORWAYPhone: +47 73594660Fax: +47 73594656

E-mail: [email protected]

Mr Hkon WoldSenior Engineer

Norwegian Public Roads Administration

P.O.Box 8142 DepNO-0033 Oslo, NORWAYPhone: +47 22073500Fax: +47 22073308

E-mail: [email protected]

ABSTRACT

This paper presents experiences with use of ETC tags for travel time registration in Norway.ETC technology can be used to collect data for estimation of travel times in the road network.

This type of data has proved to constitute a well suited basis for evaluation of traffic flowquality, and therefore well suited for traffic information and route guidance systems. It is now

possible to collect the data anonymously, so problems with protection of privacy are avoided.

INTRODUCTION

Electronic Toll Collection (ETC) systems are common in Norway, both as toll rings in smalland large cities, and as toll plazas on road sections. The worlds first ETC toll plaza wasopened in 1987, in the city of lesund, Norway. The first ETC city toll ring was the Oslo

Tolling System opened in 1990.

Those ETC systems were based on the old technology, using 856 MHz communication fortransactions. The old ETC system contained of an electronic tag, On-Board Unit (OBU),

placed inside the windshield of the vehicle and an antenna which could read the OBUidentification (number) at each toll station. The old ETC system was based on automaticdetection. Every time a vehicle passed a toll station the station number, the time and the tagidentification was recorded.

ETC is used for financing of road infrastructure in Norway. The ETC system also made itpossible to widen traffic data registrations to include section data like travel time and delay.

Delays and traffic status was calculated based on the registrations, and the information waspresented to the drivers using Variable Message Signs (VMS), Internet or the media.


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A problem with the old ETC system was protection of privacy, because each vehicle wasidentified by the tag-ID. The new ETC system is using DSRC 5.8 GHz communication link. Inthe new system it is possible to store information within the OBU. When a vehicle with an ETCtag passes an antenna, the antenna can read information from the tag, and write newinformation in the tag. Instead of reading tag identification (and identifying the vehicle), it is

now possible to store time-and-place (TAP) information in the ETC tag at one travel-timemeasurement point, and read this information at the next. The travel time is now calculatedbased on the TAPs stored in the tag, and we consider that problems with protection of privacyare avoided.

TRAVEL TIME CALCULATED BY REGISTRATION OFELECTRONIC TAG ID

SYSTEM AND TEST SITE

The first travel time registration system was developed in 1994, and a 45 km test section with4 antennas was established on E18 in the county of Vestfold, south-west of Oslo, in Norway.Every vehicle with an ETC tag was identified when passing one antenna and recognised when

passing the next antenna.

The following data was recorded at the travel-time measurement points: Station number Time Tag identification number

Approximately 30% of the vehicles traveling on the trial section were equipped with OBUs.Most of these vehicles drove the section without stopping, and the proportion was thereforeconsidered high enough to give reliable section data. Earlier studies have shown that 5-10% ofthe vehicles should be registered to give reliable results.

In the summer of 1994, a license was received, allowing registration of tagged vehicles over aperiod of three months. An on-line system for section data based on three antenna locations wasestablished. The complete tag number was recorded, so the system gave absolute recognition.

Data from each station was transmitted to the Traffic Control Centre every five minutes, sothe section data were nearly on-line. SINTEF developed a software tool for section dataanalysis. The software contains an algorithm for sorting out the vehicles with extra long traveltimes and therefore assumed to have had a stop between the registration points.

From the summer of 1995 the license terms were changed. From now on only three last digitsof the 6 or 7 digit tag identification number could legally be registered. At the same time, thelicensing requirement was released because the data collected were no longer defined as anidentification of individuals. This transition from absolute to relative recognition entailed newchallenges in tracking vehicles for calculation of section data.

VMS, DMS and Internet were used to inform the drivers about the traffic conditions. Whencongestion arises, information about actual delay and alternative routes were displayed.


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RESULTS

Analyses made of point data versus section data show that travel speed is a more stable

parameter than point speed and therefore better suited as a basis for traffic control andinformation. (Travel time and delay are calculated from travel speed).

Even in periods with unstable traffic flow on a section, there is little variation in travel speedfrom one vehicle to the next, therefore the travel speed is a useful indicator of the traffic flowquality.

To illustrate the variation in point speeds and in travel speeds on a long section, the 35 kmsection (Tnsberg - Sande) and the registration point at Sjskogen (25 km north of Tnsbergand 10 km south of Sande) are shown in the figure below. In addition to the average pointspeed for the last 5 minutes, a smoothed point speed is also included to be compared to the

travel speed. Here smoothed point speed means a weighted average over the last 30 minutes.

Figure 1 Point speed at Sjskogen and section speed between Tnsberg and Sande.

Point and Section Speed

Sunday 26.06.94

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10

20

30

40

50

60

70

80

1215

1240

1305

1330

1355

1420

1445

1510

1535

1600

1625

1650

1715

1740

1805

1830

1855

1920

1945

2010

2035

2100

2125

2150

2215

2240

2305

2330

Time of Day

Speed[km/h]

Vpoint

Vpoint smoothed

Vsection


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ANONYMOUS TRAVEL TIME REGISTRATION

The ETC technology offers an extensive infrastructure in Norway. Nationwide 1 millionvehicles are equipped with OBUs, which is approximately 40% of the carpool. About 95% ofthe cars travelling through the Oslo toll ring in rush hours are equipped with OBUs.

There are toll rings in Oslo, Tnsberg and Kristiansand, in addition to toll plazas on E18between Oslo and Kristiansand. This gives a high proportion of equipped vehicles, and a verygood basis for using ETC technology for calculating travel times.

Norwegian Public Roads Administration has now developed functionality for anonymoustravel time registration and calculation based on the new ETC system. The systemfunctionality is basically to store time-and-place (TAP) information in the OBU at one travel-time measurement point (TTMP), and read this information at the next TTMP, before a newTAP is stored in the OBU. Based on the TAPs stored in the OBU, the travel time can becalculated.

SYSTEM OVERVIEW

The travel time system can be divided into three parts as shown in figure 2.1. The travel time information system2. The network3. The travel time measurement point (TTMP)

Figure 2 The travel time system.


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The data are stored in the travel-time information system and an average 5-minutes traveltime is calculated. Vehicles that have stopped between two TTMP are sorted out beforeaggregating the data. Information about average 5-minute travel time is given the driversthrough VMS, DMS, Internet and media.

The network is a private network not open to the public preferable solved by configuration ofthe routers only communicating with other known routers, and it is built with fixed lines. Thenetwork is used to configure the antennas at the TTMPs, and to transmit registered data fromantennas/OBUs directly to the TTM server.

Timing between the measurement points is crucial and needs synchronization. The NetworkTime Protocol (NTP) is used to synchronize the time at the antennas from the TTM server.

NTP is a protocol designed to synchronize the clocks of computers over a network.

At the TMMP the antenna is communicating with the OBUs through DSRC link. Every time avehicle with an OBU passes an antenna, the travel time data is read and transmitted to the

TTM server via ADSL line.

The Road Side Equipment (RSE) consists of an antenna, microwave electronics circuitry anda real-time computer. The unit provides a direct interface between the air interface to the tags(ISO 14814 delta) and the local system (ISO 14814 beta). The operating frequency of theantenna is 5.8 GHz. The unit is compliant with the EN 300 674, and it is type approved inaccordance with I-ETS 300 674.

The On Board Unit (OBU) is a 5.8 GHz DSRC Transponder designed for automaticregistration of vehicles. It communicates with the antenna or other reader equipment designedto meet all standards related to Road Traffic and Transportation Telematics (RTTT).

SYSTEM FUNCTIONALITY

The system functionality is basically to store time-and-place (TAP) information in the OBU atone travel-time measurement point (TTMP), and read this information at the next TTMP,

before a new TAP is stored. Based on the TAPs stored in the OBU, the time of travel may becalculated. The writing of TAPs inside the OBUs must not affect the toll collection system.Under no circumstances will the OBU-ID be read or stored.


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DynamicDatabase

Travel-timemeasurement point 2



Tolling Station

Internett, TCC, VMS, DMS, SMS/MMS

Figure 3 Illustration of the test site for the travel time registration system.

As the vehicle passes TTMP 1:1. The TTMP will read the TAPs for travel time calculation.2. The TTMP will overwrite the oldest TAP with a new TAP3. The TTMP will communicate the TAPs to the TTM server for travel-time calculations

As the vehicle passes TTMP 2:1. The TTMP will read the TAPs for traveltime calculation.2. The TTMP will overwrite the oldest TAP with a new TAP3. The TTMP will communicate the TAPs to the TTM server for travel-time calculations

As the vehicle passes a tolling station:1. An ordinary ETC transaction is executed2. The log pointer is incremented

As the vehicle passes TTMP 3:

1. The TTMP will read the TAPs for traveltime calculation.2. The TTMP will overwrite the oldest TAP with a new TAP3. The TTMP will communicate the TAPs to the TTM server for travel-time calculations

The XML-string from the TTMP to the TTM server will be like:


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As long as we just use the TAPs, and not any OBU identification, no vehicles are identified.Therefore, we consider the system for anonymous.

TEST SITE

An important part of the travel time system is to test and evaluate the functionality in realtraffic. Therefore, a test site equipped with 14 antennas (7 in each direction) is established ona 120 kilometer long section of highway E18 in south-eastern Norway. The test section goesfrom Oslo to Larvik through the counties of Akershus, Buskerud and Vestfold. This is aroad with high traffic density and traffic congestion problems.

The test section consists of a 4 and 6 lane freeway from Oslo to Horten (about 75 km) and a 2lane highway from Horten to Larvik (about 45 km). We have only one antenna in eachdirection, even on multilane freeways. The antennas are located above the right lane.

Location Distance between antennas [km] Road section

OsloLierskogen 19.5 4-6 lane freewayDrammen North 11.5 4 lane freewayDrammen South 8.0 2-4 lane freewayHorten 36.0 4 lane freewayTnsberg 15.5 2 lane highwayLarvik 29.5 2 lane highway

Table 1 Location of antennas in southbound direction.

Figure 4 Picture from the location Drammen North.

The proportion of vehicles with OBU varies over the test section. Near Oslo the proportion is

very high (about 90%), and in the south near Larvik the proportion is down to about 60%.This is still more than enough for travel time purposes.


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TRAFFIC INFORMATION SYSTEM

The main purpose of the travel time registrations is to inform travellers about the currenttraffic situation between Oslo and Larvik. Information will be provided through:

1. The Internet

2. Media3. VMS / DMS

INTERNET SOLUTION

The main purpose of the web site is to inform readers about the current travel time and trafficsituation between Oslo and Larvik.

The following information is available on the Internet:

Travel time in both directions for the section between Oslo and Larvik (updated every 5minutes) Travel time in both directions for different sub-sections between Oslo and Larvik (updated

every 5 minutes) Travel time forecasting Information about alternative routes Updated information about closed roads, traffic status and road works Tracing of vehicles from the transport company Linjegods with GPS/GSM (Only

available with password)

MEDIA

An important target group who could distribute traffic information to the travellers are theradio stations. Several channels have special programs with traffic information, and theinternet page is one of their information sources.

VARIABLE MESSAGE SIGN AND ROUTE GUIDANCE SYSTEM

Along the road information will be given to the drivers through variable message signs /

dynamic message signs informing about the traffic flow conditions. So far all the signs arelocated in the southern part of the test section (Larvik-Horten) where there also are routeguidance systems showing the drivers alternative routes.

The variable message signs are controlled from the Traffic Management Centre. We use twodifferent kind of variable message signs:

1. Signs with qualitative information Possible Congestion Long Delays Accident on E18


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REFERENCES

[1] Eriksen T., Giver T. and Haugen T. : Traffic Control and Information towards theYear of 2000. Final Report. SFT63 A 95011. SINTEF Civil and EnvironmentalEngineering, Transport Engineering. Norway 1995.

[2] Haugen T. : The Section Data Project. Analysis of Point and Section Data. SFT22 A96605. SINTEF Civil and Environmental Engineering, Transport Engineering.

Norway 1996.

[3] Haugen T. : Traffic Information on E18. Evaluation of the VMS signs.SFT22 A 97608. SINTEF Civil and Environmental Engineering, TransportEngineering. Norway 1997.

[4] Haugen T. and Giver T. :Improving Traveller Information and Route Guidance byUse of Automated Vehicle Recognition. Paper. 5th Wold Congress on ITS. Seoul,Korea 1998.

[5] Q-Free. : System specification for travel-time measurement system using MD5850 andMD5885. Q-Free document number 2003-635-112-04. Norway 2004.

[6] Wold H. : Traffic Information on E18 in Vestfold

[7] Wahl R., Fl M., Haugen T., Bang B. and Lillestl P. :Dynamic TransportInformation - State of the art. SFT22 A03305. SINTEF Civil and Environmental

Engineering, Roads and Transport. Norway 2003.

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Paper ETCTag