Blind and sighted pedestrians’ judgments of

gaps in traffic at roundabouts

Student:董瑩蟬

Purpose• This paper employed blind and sighted

pedestrian to take two experiments.

• The first experiment was investigated the better road crossing time at three different vehicle volume of roundabout. They collect the gap on the three site, and the crossing behavior of two group.

• The second experiment was the driver stop in from of the subjects or not. And collect the data at the three style road, that want to know the different road while the driver has different behavior.

Reference

•There are many road of this type on the world. (Brilon,1991; Brown,1995;jacquemart,1998)

Reference• There are many studies to care the older and children on t

he road safety.(Crawford,2002;U.S.Access Board,2001/2003 ) • Some studies conclusion the single-lane may safety for pe

destrian on the traditional intersections. (Alphand et al.,1991;Brude & Larsson,2000;ect.)

• There increased different between vision and heard judge when the vehicle become quiet.(Barthorpe,2000;Zorpette,2004)

• Blind pedestrian used cane that can increase visibility for oncoming vehicle.(Jacobson,1993)

Method 1• Subjects

– 12 person include 6blind(3used dog guides and 3used long canes) and 6 normal vision

– Age between 23 to 56 years

• Site– Towson: double-lane, traffic volume 40000 vehicle– Annapolis: double-lane, traffic volume 24000 vehicle– UMBC: single-lane, traffic volume 12000 vehicle

• Equipment– Note book computer– button

1msighted

blind

Method 1

• Independent variable– Group: blind and sighted – Site: three different roundabouts – Lane: entry and exit

• Dependent variable– Traffic characteristics: Vehicle volume, gap duration– Safety margins– Latency to detect a crossable gap– Overall reporting of crossable gap

Method 1• Process

– The data collect from 9 A.M to 4 P.M– Look the traffic situation about 3 to 5 min– Normal walking speed from sidewalk to

splitter island at least four 4 time– Each trial lasted 2 min, and subject response

“go” or ”stop”, at the same time they press the button

Results- Traffic characteristics•The Type error ∣ rate was significant (loss) P<0.05.•The data analysis follow Keppel (1991) and Howell (1992).•The mean vehicle volume was 3 to 13 vehicles/min•The average vehicle volume was significantly different on the three site.(F(2,175)=198.76)

•The interaction of vehicle volume between lane and site at the UMBC and Annapolis (F(2,175)=15.87)•The vehicle volume of entry lane significant more than exit lane(F(1,175)=47.82)

Results- Traffic characteristics•The average gap vary counter to the vehicle volume•The mean gap duration with 20, 7 and 5 second at UMBC, Annapolis and Towson.• The gap duration of UMBS significantly longer than other sites. (F(2,173)=41.52)

•The site and lane has interaction (F(2,173)=8.15)•The gap duration of exit lane significantly longer than entry at UMBC(F(1,173)=22.7)

Results- Traffic characteristics

Results -Traffic characteristics

• The left of dotted line mean unsafe crossing the road.

• If the fast walking pace, the dotted line move to the left.

Results-Safety margins

Results-Safety margins

Results-Safety margins• The negative safety margin of blind more than

sighted’ person, specially on Towson and Annapolis.

• The safety margin of blind was shorter than sighted’ person, at Annapolis with Z=2.065 and at Towson with Z=6.606.

• According to site and lane, the rare of sighted’ person unsafe crossing time was 13.4%, and blind was 28.9%

• The rare of safe crossing/unsafe crossing with blind was 2.46, and 6.46 with sighted; the sighted significantly more than blind(2.64)χ2(1) = 50.38.

Results- Latency to detect a crossable gap• The lane significantly

different on the gap detection(F(1,333)=21.26), the entry lane was 2.8s, and the exit was 3.8s.

•The blind mean detection was 4.8 s, the sighted was1.9s; may blind may heart the sound longer than sighted.•The vision status has significantly different for the gap detection latency (F(1,335)=120.28).

Gap detection latency site 3.5second UNBC 3.4second Annapolis 3.1second Towson

Results- Overall reporting of crossable gap

Results- Overall reporting of crossable gap

• Overall, the miss rare with blind more than sighted’ pedestrian.

• The has significantly different on the percentage of crossable gap at three site. Sighted χ2(2) = 60.86, and the blind χ2(2) = 41.15

• The entry lane significantly better than exit with blind wasχ2(1) = 40.52; and sighted was χ2(1) = 35.76

Discussion• The vehicle volume was an important

factor with pedestrian crossing the road.

• UMBC’ decision gap was different with other cities.

• The safety crossing gap was small at Towson and Annapolis, and must to be fast to cross the road.

• The negative safety margin was fewer at UMBC.

Discussion• The blind spent more time (about 3 second) than

sighted to crossing the road, that because blind must to heard vehicle sound front of traffic noise.

• The pedestrian decision without vision may higher risk on the road crossing.

• The blind often used sound judge the traffic situation, but the sighted used the vehicle speed and distance.

• All subject reported that they often change attention at the different traffic situation.

Method 2• Subjects

– 14 person include 10 blind(5 used dog guide and 5 used long-cane) and 4 normal vision.

• Site– Roundabout: single-lane, 200vehicle/hr– Campus: two-lane, 180vehicle/hr– Downtown: two-lane, 260vehicle/hr

• Independent variable– Site-three area – Device-long cane or dog guide– The car stop or not

Method 2• Process

– The data collect from A.M.9 to P.M.4– Trial sequence used counterbalanced ,the

blind half trial used device (long cane or dog guide) and the other half trial that used no device.

– In the roundabout ,the half of trial complete at exit lane, and other at entry lane.

– In other sites trial complete on each roadside.– This experiment add variable that the driver

stop or not.

Results

Results• The data used spss log-linear model analysis.• The car outcome has significantly different at sit

e.χ2(3) = 214.05• The car outcome has significantly different betw

een the pedestrian device. χ2(2) = 6.97• The driver tend to stop in front pedestrian at the

campus. But this situation was few at Downtown.

• The driver tend to stop at entry in the roundabout χ2(1) = 93.8, that because the vehicle speed slower, the driver can look the pedestrian.

Discussion

• The driver stop rare increased 15 to 32 percentage when pedestrian used device.

• There was an potential problem when driver can’t accurate stop in from of pedestrian. (Harrell,1992)

• Some studies improve pedestrian safety issues. (Huang,2000)

Conclusion• This paper showed that the blind has few

chance to crossing road. They decision time more longer than normal vision. The delay time about 3 second.

• The blind pedestrian has higher risk than normal vision person.

• They found that the blind pedestrian difficult to judge the road situation and they risk higher than normal vision.