detection distance and glare of headlamp sys- tems with ... · pdf filedetection distance and...

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Detection Distance and Glare of Headlamp Sys-

tems with ADB-Functions

Bastian Zydek, Christoph Schiller, Max Wagner, Dmitrij Polin, Prof. Tran Quoc

Khanh, Laboratory of Lighting Technology, Technische Universität Darmstadt

This research of the University Darmstadt focuses on the quantification of the

abilities of such systems in terms of detection distance and potential glare for

other road users. For this purpose, two vehicles were tested. The first one is a

series vehicle with HID with ADB-functions. The second one is also a series vehicle

with non-adaptive standard halogen headlamps. This approach allows comparing

five headlamp functions:

Table 1: Tested Headlamp Functions

Lamp Type Headlamp Functions

HID Passing beam Driving Beam

Glare-Free High Beam

Halogen Passing Beam Driving Beam

Method

As described in Table 1, two vehicles were tested. Both vehicles are series vehi-

cles. One with HID headlamps and activatable Glare-Free High Beam, realized by a

specially shaped drum in the HID projection module. The second vehicle was

equipped with standard halogen reflection headlamps. Both vehicles were aimed

correctly before the execution of the tests.

The tests were conducted on the runway of the August Euler Airport in Griesheim,

Germany under controlled conditions (see figure 1). In total three parameters

were tested for each headlamp function (see Table 1):

Discomfort glare

Disability glare

Detection distance

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Figure 1: Runway of August Euler Airport

To realize a good comparability, all three parameters were tested at the same

time. Meaning that while a subject was driving a test vehicle to perform a detec-

tion test with a certain headlamp function additional subjects were positioned in

oncoming vehicles to give a measure for disability and discomfort glare. This pro-

cess is hereinafter called “run”. Five vehicles did participate in each run (see figure

2). Four vehicles were positioned as static oncoming vehicles (0 km/h). The fifth

vehicle was one of the two test vehicles, which was driven with one of the five

headlamp functions being activated with a constant speed of 80 km/h. The four

oncoming vehicles were placed with a distance of 180 m to each other. The lane

width was set to 3.5 m. The first oncoming vehicle acted as a calibration vehicle

setting the headlamp system of the test vehicle in a defined status when approach-

ing the other oncoming vehicles.

The tests were performed on four test-days under complete darkness. For each

test-day the participation of seven subjects, one software administrator, one de-

tection object administrator and one examiner was necessary.

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Figure 2: Test Setup

Discomfort glare

In each run, a total number of four subjects did perform a discomfort glare rating

on the de Boer scale (see figure 3). The subjects were positioned as driver and co-

driver in the second and third oncoming vehicles (see figure 2). The subjects

were advised to give one rating for one run / passing process. During the runs, the

subjects did not know which vehicle and activated headlamp function would pass

them.

Figure 3: De Boer rating on questionnaire

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The following table shows the involved number of subjects and ratings:

Table 3: Subjects and ratings, detection distance

Lamp Type Headlamp Functions Subjects Ratings

HID Passing beam 16 102 Driving Beam 16 102

Glare-Free High Beam 16 102

Halogen Passing Beam 10 77 Driving Beam 10 85

Disability glare

Disability glare quantification was performed in the last oncoming vehicle by two

subjects in driver and co-driver seating position. Both subjects fulfilled a thresh-

old contrast test during each run. Threshold contrast is the smallest percep-

tible contrast, meaning that one is just able to differentiate an object with a lumi-

nance from its surrounding luminance . Threshold contrast increases in

the presence of a glare source making it a measure for disability glare. The in-

crease of threshold contrast can be explained by the fact, that the glare source

generates visible light scattering. This scattering arises in eye media and is de-

scribed by a so called veiling luminance . This veiling luminance adds itself to

the object luminance as well as to the surrounding luminance (see figure 4). The

consequence is, that the contrast between object and surrounding decreases

which in return has a threshold contrast increment as a result.

Figure 4: Contrast decrease in presence of glare

What is special is that the threshold test is carried out constantly during each run

meaning that the subjects have to adjust the threshold contrast continuously dur-

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ing each passing process. To fulfill this task two “threshold contrast boxes” were

build (see figure 5).

Figure 5: Threshold contrast boxes

The threshold boxes were positioned in front of the vehicle with a horizontal an-

gle of 2.5° to the detection object. This is equivalent to an object on the right side

of the road at 80 m distance. The object itself is round with a diameter of 0.5°.

The task for the subjects was to adjust the contrast continuously. To realize a vari-

able contrast the threshold contrast boxes contain a dimmable LED. The LED rep-

resents the object with which had to be adjusted in brightness to be just per-

ceptible. To realize a quick reaction of the subjects, the test was designed so that

the brightness increases automatically by 1.5 % every 200 ms. The subjects had

the task to push a button as soon as the object is visible. When pushing the button

the object luminance decreases by 6 %. The distance to the moving test vehicle

was measured by a GPS system. This enabled the authors to match the distance

data to the corresponding threshold contrast. The procedure is visualized in the

following figure:

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Figure 6: Dynamic threshold contrast







Detection distance

Detection distance is the distance from the point of the detection of a relevant

object to the object itself. The sooner a driver detects an object the more time

she/he has for a certain reaction. During one run two objects had to be detected

which could appear at three possible positions. All objects were painted to have

the same reflection characteristics, which were also checked by luminance meas-

urement (see figure 7).

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Figure 7: Detection objects

The task for the subjects was to drive with 80 km/h and to push a button as soon

she/he detects an object. By the use of a GPS system, the distance to the detected

object could be calculated.







4 Results and Discussion

In this chapter, one can find the results of this investigation. It is important to

remind, that the results for driving beam are only presented for reference. Static

driving beam is generally not activated in an oncoming traffic situation such as it

was tested in this investigation.

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Discomfort glare

The following figure shows the average de Boer rating for each headlamp function

(see table 1). The bars represent the simple standard deviation. The average

values for Halogen passing beam, HID passing beam and HID glare-free high beam

are better than 7.0 (better than satisfactory) on a similar level. This result indi-

cated that the discomfort glare of Halogen lamp and HID lamp headlamps are not

different if the headlamps are correctly adjusted.

Figure 8: Discomfort glare rating

Disability glare

The following figures 9 and 10 show examples of dynamic threshold contrasts

with the corresponding distances. The thick line represents the mean curve. To

compare the different headlamp functions the mean threshold contrast (mean of

thick line) for the distance range of 1000 m to 0 m has been computed. The results

are visualized in the following figure 11. The mean threshold contrast of Halogen

passing beam (5.8), HID passing beam (6.3) and HID glare-free high beam (6.5)

are on the similar level (the difference is statistically not significant).

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Figure 9: Threshold contrast: Halogen, passing beam (driver)

Figure 10: Threshold contrast: Halogen, driving beam (driver)

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Figure 11: Mean threshold contrast from 1000 m – 0 m (driver & co-driver)

Detection distance

The following figure shows the mean detection distance for each headlamp func-

tion. The bars represent the simple standard deviation.

Figure 12: Mean detection distance

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Conclusion

The test described in this paper had the objective to determine the abilities of new

headlamp functions on the basis of glare and detection. This was realized by quan-

tifying detection distance, disability glare and discomfort glare as well as by the

participation of a relative large amount of subjects.

The results of the tests allow drawing three main conclusions:

- The presented test concept shows a clear separation of different head-

lamp functions. Especially the gathering of dynamic threshold contrast

turned out to be a very good method to quantify disability glare in dy-

namic driving situations.

- The passing beam of well-aimed halogen and HID headlamps does almost

not differ in discomfort and disability glare. In contrast to that, HID head-

lamps realize a substantial increase in detection distance.

- In comparison to passing beam, produces a well-designed Glare-free high

beam almost no increase in disability and discomfort glare while realizing

a clear increase in detection distance.

It is important to note, that the presented results are based on two vehicles as well

as on one certain traffic situation. Therefore, further tests shall be done in the next

winter 2014-2015 with more modern car types.

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