**8. References**

24 Modern Metrology Concerns

Proposed test protocol is divided into a part of recording the individual measurements and a part of evaluation of the application as a whole, including evaluation of system parameters. It is already possible on the basis of pilot testing to summarize the partial results and define partial requirements for selected system parameters of tested

a. **Accuracy** – the required value of 15 meters in the horizontal plane at 95 % level of probability. Thus defined accuracy corresponds to usual accuracy requirements on OBU GPS unit using a standard statistical distribution of signal parameters. The tested OBU and its software configuration were selected based on the required accuracy.

b. **Reliability** – the specific desired value will be defined on basis of experience in the follow-up testing. Assuming a value of around 90 %, eventually higher, at 95 % probability level. After pilot tests result with 60.4 % success of virtual gate passage detection can be seen that the higher reliability will be required for the approval. To approve the usage of tested OBU it will be necessary to adjust the software in OBU or to

d. **Continuity** – for telematics application this is not a critical system parameter. Depends on ability of the telematic system to assess and calculate the travelled route in case of system failure while driving the vehicle; this parameter does not depend only on the OBU and GNSS signal reception. In case of the usage of virtual sections or more virtual gates on the road sections the requirements on this parameter are significantly

e. **Integrity** – this parameter has not been considered for the tested systems, mainly because it represents rather the quality of OBU diagnostics, resp. informing the user within a reasonable time for failure of proper OBU function. This parameter is not so much related to position determining or frequency of the virtual gates and sections

f. **Safety** – "dangerous conditions" are defined for both tested applications in the field of electronic toll system (EFC). This is a situation where the system assesses charges, which in fact did not occur. This is part of the conditions to test status "failed" – socalled "false alarms" – i. e. the identification of neighbouring gates or division, identification or evaluation of multiple transits the same gate or the same road section. With regard to safety (as one of the important system parameters of tested applications) appropriate testing scenarios were selected by pilot tests – all the scenes are containing unpleasant situation in a similar gate on nearby parallel road (i. e. identically oriented and situated at a distance of tens of meters from the passing road). It should be emphasized that effort to eliminate false alarms is associated with a reduction on the reliability parameter of applications, i. e. reducing the probability of passed gates/sections correct detection. It is therefore necessary to seek to balance, which on the one hand significantly reduces the risk of false positives, on the other hand, provides useful reliability parameter. This balanced condition can be found by testing

various OBU units, resp. by testing one OBU at various software settings.

use another OBU. Reliability is affected by the security parameter, see below. c. **Availability** – the specific desired value will again be defined on the basis of experience in further testing. Assuming the OBU unit activation at start-up of travel and the availability value up to 60 seconds. Pilot testing showed in most cases the availability of

Accuracy of the OBU can be further increased.

applications:

tens of seconds.

decreasing.

passage records.

	- [http://www.caspur.it/risorse/softappl/doc/sas\_docs/qc/chap1/sect19.htm]
