Obstacle Detection: Investigating the effects of lamp type and
Dates: June 2007-May 2008
Staff: Steve Fotios, Chris Cheal
Funding: Philips Lighting Ltd.
Fotios SA & Cheal C, Obstacle detection: A pilot study investigating the
effects of lamp type, illuminance and age, Lighting Research & Technology, 2009;
Fotios S &
Cheal C, Lighting Spectrum And Obstacle Detection For Pedestrians,
Lux Europa, Istanbul, 2009, 1171-1176
Fotios S & Cheal C, Lighting Spectrum and Obstacle Detection for Pedestrians,
Proc. of the 6th Lux Pacifica, Bangkok, 23-25 April 2009,
Fotios S & Cheal C, Lamp Spectrum, Illuminance and the Pedestrianís
Ability to Detect Obstacles, Lighting Journal, 2008; 73(6); 35-41
examined the effect of light source, illuminance and observerís age on the
ability to detect an obstacle simulating a raised paving slab, presented for
300 ms in six different positions relative to the line of fixation.
The light sources used were the high pressure
MASTER City White 942 (4200K) and MASTER CosmoWhite (2700K) discharge
The illuminances used were 0.2, 2.0 and 20 lux, measured on the
paving surface. These illuminances cover the range of those recommended for
subsidiary streets and ensure the human visual system is operating in the
mesopic state. Two age groups were used as observers, one group being less
than 45 years of age and the other being more than 60 years of age. The
positions of the obstacle varied from 0 to 42 degrees to the right of
fixation and 8 to 23 degrees below fixation.
The figure below shows the test apparatus: this is a side elevation with the
panel removed to expose the interior.
The data collected were
used to determine the height of the obstacle above the paving surface
required for fifty percent detection at each position, for all combinations
of light source, illuminance and age. From these detection heights it was
Obstacle detection was influenced by the illuminance, the 50% detection
height being less at 20 lux than at 0.2 lux.
At 0.2 lux, the 4200K MASTER City White light source gave the smallest 50%
detection height while the high pressure sodium light source gave the
largest. There were no statistically significant differences between the
50% percent detection heights for the three light sources at 2.0 and 20
The young observers showed the smaller 50% detection height at 0.2 lux
but at 20 lux there was no difference in 50% detection height for the
two age groups