revtothelimit - motorbike forum

I was discussing the circumstances of my most severe RTA with someone and said about the halo effect (bouncing up and down headlight can trick the brain into thinking you're approaching much slower than you are) but I can't seem to find an article or proper description online.
I keep getting details of trendy headlight surrounds and not what I am looking for at all.

Any help from the knowing please!

I've never heard of the halo effect, but it's very well known that headlights can make approaching vehicles speed very hard to judge. Much more so than just seeing a vehicle itself.

Nordboy wrote: Thu Nov 20, 2025 8:13 am I've never heard of the halo effect, but it's very well known that headlights can make approaching vehicles speed very hard to judge. Much more so than just seeing a vehicle itself.

I'm not 100% sure it's called the halo effect any more after struggling to find it online and now a man of your experience never having heard of it!

Hopefully Horse or SpinDoc still frequent the forum, they should make sense of what I'm on about hopefully

You called?

Whatever the name, I've not heard of anything similar.

I did read something, years ago, about over- and under-estimation of speed - but I've not found a reference since

There has been plenty of research on difficulties of assessing the speed of a single headlamp. Google "Mark Gould Thesis, Royal Holloway" and "time to arrival illusion" (which TfL used for a road safety video).

Potentially that leads drivers to see you, then either just pull out, or wait, then think "oh, not here yet, loads of room ... "

There's also the bump-flash issue, you hit a bump and your dipped beam which has been shining down then is visible to the driver. They think you're being kind, so pull out.

Could this also apply to rear lights on a vehicle? Some brake lights flash quickly when hard braking happens. This could also potentially cause the halo effect I suppose.

I remember Voyager on VD used to claim that having your headlight on made the bike harder to see

I find it best to observe any hazards well in advance. Then apply the brakes in good time.

Le_Fromage_Grande wrote: Thu Nov 20, 2025 4:28 pm I remember Voyager on VD used to claim that having your headlight on made the bike harder to see

Under some circumstances, possibly.
https://en.wikipedia.org/wiki/Yehudi_lights

MyLittleStudPony wrote: Thu Nov 20, 2025 4:59 pm I find it best to observe any hazards well in advance. Then apply the brakes in good time.

Yup

Claiming 'priority' or 'right of way' is of little comfort if you end up as a bleeding, crumpled, pavement pizza.

Horse wrote: Thu Nov 20, 2025 5:01 pm

MyLittleStudPony wrote: Thu Nov 20, 2025 4:59 pm I find it best to observe any hazards well in advance. Then apply the brakes in good time.

Yup

Claiming 'priority' or 'right of way' is of little comfort if you end up as a bleeding, crumpled, pavement pizza.

Amazing how many cars still call priority (if they had a voice) in the face of a 19T bus!! Principle is the same, but slightly more protection (although I wouldn't argue with a bus if driving a car, or any vehicle really!!)

MyLittleStudPony wrote: Thu Nov 20, 2025 4:59 pm I find it best to observe any hazards well in advance. Then apply the brakes in good time.

Then finesse the clutch bring it up to 12 o'clock and up through the gears?

Horse wrote: Thu Nov 20, 2025 8:40 am You called?

Whatever the name, I've not heard of anything similar.

I did read something, years ago, about over- and under-estimation of speed - but I've not found a reference since

There has been plenty of research on difficulties of assessing the speed of a single headlamp. Google "Mark Gould Thesis, Royal Holloway" and "time to arrival illusion" (which TfL used for a road safety video).

Potentially that leads drivers to see you, then either just pull out, or wait, then think "oh, not here yet, loads of room ... "

There's also the bump-flash issue, you hit a bump and your dipped beam which has been shining down then is visible to the driver. They think you're being kind, so pull out.

Samuel J. Levulis, Patricia R. DeLucia, Jason Jupe, Effects of
oncoming vehicle size on overtaking judgments, In Accident
Analysis & Prevention, Volume 82, 2015, Pages 163-170, ISSN 0001
4575, https://doi.org/10.1016/j.aap.2015.05.024.

"The purpose of the current study was to determine whether overtaking judgments are
influenced by the size of an oncoming vehicle, and by whether a driver actively conducts an
overtaking maneuver or passively judges whether it is safe to overtake. We hypothesized that the
size of an oncoming vehicle would influence overtaking decisions because rate of optical
expansion is below threshold during high-speed overtaking, putatively leading participants to
rely on perceived distance and velocity. Results of Experiment 1 supported this hypothesis:
participants accepted more gaps as safe, and committed more false alarms, when the oncoming
vehicle was a motorcycle than a car or large truck, consistent with previous reports of the size
arrival effect on driving-related judgments (Caird & Hancock, 1994; Horswill et al., 2005). "

https://ttu-ir.tdl.org/server/api/core/ ... c9/content

Le_Fromage_Grande wrote: Thu Nov 20, 2025 4:28 pm I remember Voyager on VD used to claim that having your headlight on made the bike harder to see

Anecdotally, when the local lackwit on the BMW GS comes along the road with both main beam and auxiliary LEDs set on stun, it's easy to see the bike's lights, right up to the moment they're aimed straight at you, then you're blinded... even in daylight! After that, all you can see is the glare which a bike lurking somewhere behind it.