Design Rationale for DRL Behavior
Thread Starter
Driver School Candidate
Joined: Mar 2017
Posts: 11
Likes: 1
From: California
Design Rationale for DRL Behavior
What is the design rationale wherein either left or right daytime headlights will turn off when the corresponding turn indicator is turned on? I've noticed this behavior a few times in newer car models, specifically Audis.
CL Community Team
Joined: Aug 2006
Posts: 12,523
Likes: 216
From: San Francisco, CA
The rational is that the bright white DRL could detract from the visibility of the turn signal, thus making it potentially dangerous for oncoming traffic. However, it varies per automaker.
Last edited by RXSF; Jul 15, 2017 at 11:03 PM.
Instructor
Joined: May 2015
Posts: 780
Likes: 120
From: MA
-Mike
Lexus Test Driver
Joined: Aug 2014
Posts: 1,397
Likes: 51
From: CN
Audi, Ford, Jaguar, so far. What's distracting is that they seem to use the same array for DRLs and indicators so the switchover is distracting. Dynamic KITT indicators make things even worse. I prefer having DRLs and indicators separated.
Last edited by chromedome; Jul 15, 2017 at 11:53 PM.
Lexus Fanatic
Joined: Oct 2003
Posts: 94,328
Likes: 236
From: Virginia/D.C. suburbs
Drgrant is correct. It's generally a shared-light issue. Some states have laws saying that headlights or DRLs must be on when using wipers in bad weather or visibility is less than 500 feet. This set-up (apparently) satisfies those laws, even though only one headlight/DRL is on when the turn-signals are blinking. At least I haven't heard of anyone getting a ticket (yet) for that.
Lexus Test Driver
Joined: Sep 2016
Posts: 8,574
Likes: 390
From: PA
I thought someone says there was a reg that if the drl is within x " or cm of the turn signal it had to do that, but my BMW as an '07 has cornering lamps which would actually do the opposite, light up even brighter when the turn signals are on (actually they operate indendently but we're assuming one signals when turning)....
Trending Topics
Lexus Fanatic
Joined: May 2012
Posts: 68,483
Likes: 3,995
From: Maryland
Originally Posted by mmarshall
Drgrant is correct. It's generally a shared-light issue. Some states have laws saying that headlights or DRLs must be on when using wipers in bad weather or visibility is less than 500 feet. This set-up (apparently) satisfies those laws, even though only one headlight/DRL is on when the turn-signals are blinking. At least I haven't heard of anyone getting a ticket (yet) for that.
The point really is rear marker lamps. Rear lamps don't illuminate with the DRLs.
When they say "headlights need to be on", they mean headlights.
http://www.santacruzlive.com/streets...lights-on-law/
http://www.city-data.com/forum/new-j...ticket-if.html
ClubLexus Stories
Celebrating Lexus & Toyota from Around the Globe
8 Tips for Improving Your Hybrid or Plug-in Hybrid's Efficiency!
Michael S. Palmer
10 Best Lexus Models No One Remembers
Joe Kucinski
TRD Off-Road Premium: Best 2026 4Runner, Except This One Thing
Michael S. Palmer
Top 10 Lexus & Toyotas to Drive Before You Die!
Joe Kucinski
Top 10 Lexus/Toyotas With The LEAST 5-Year Depreciation
Joe Kucinski
Lexus LC500 Convertible Auction: A Preview of Rising Values?
Brett Foote
GX 550 vs TX 550: Best 3-Row Luxury Lexus Family Hauler
Michael S. Palmer
9 Best Lexus Models You Can Buy for Half Price (And 1 You Shouldn't!)
Joe Kucinski
2026 Lexus NX Buyer's Guide: Models, Features, Prices & More!
Brett Foote
CL Community Team
Joined: Aug 2006
Posts: 12,523
Likes: 216
From: San Francisco, CA
I tend to agree but I love how Mercedes has the DRL fade back on instead of the abrupt switch back
Lexus Test Driver
Joined: Aug 2014
Posts: 1,397
Likes: 51
From: CN
Well, it looks like different Ford models do things differently. The top spec Mondeo/Fusion with the KITT indicators has the DRLs turn off when the indicators are on, but lower spec models keep the DRLs on while the static indicators light up.
The problem is that having both DRLs and indicators so close together and lit at the same time means the indicators aren't clearly visible, but having them light up dynamically is even more distracting. Fading DRLs are also a distraction because the fading is interpreted as movement by the human brain and the driver ends up focusing on that. It's much easier to tune out static or slowly blinking lights and focus on the surrounding traffic.
It's going to be a bigger issue in the future with much smaller headlamp units that use LEDs for the main and high beams. There won't be much space so designers could cram everything together. I can imagine the cognitive horror of a road full of car lights blinking like neon caterpillars on a dark, rainy night...
The problem is that having both DRLs and indicators so close together and lit at the same time means the indicators aren't clearly visible, but having them light up dynamically is even more distracting. Fading DRLs are also a distraction because the fading is interpreted as movement by the human brain and the driver ends up focusing on that. It's much easier to tune out static or slowly blinking lights and focus on the surrounding traffic.
It's going to be a bigger issue in the future with much smaller headlamp units that use LEDs for the main and high beams. There won't be much space so designers could cram everything together. I can imagine the cognitive horror of a road full of car lights blinking like neon caterpillars on a dark, rainy night...
Last edited by chromedome; Jul 16, 2017 at 09:16 AM.
Pole Position
Joined: Jul 2010
Posts: 2,944
Likes: 182
From: Los Angeles, CA
i have yet to see this and I pay really close attention to the cars around me. Now I want to drive around until I find the feature.
Advanced
Joined: Jun 2017
Posts: 517
Likes: 44
From: Earth
I think it looks tacky and cheap when the LED DRL goes black to make way for an ancient halogen turn signal. If the purpose for these lights is increased visibility and safety, why not use a full LED turn signal assembly instead of halogens?
When I see Audi models with turn signals on it always seems to anger me for the reasons mentioned
When I see Audi models with turn signals on it always seems to anger me for the reasons mentioned
Lexus Fanatic
Joined: Oct 2003
Posts: 94,328
Likes: 236
From: Virginia/D.C. suburbs
The laws do mention headlights with wiper-use, but they don't mention taillights. DRLs, on most vehicles, use the same bulbs as regular headlights (without taillights), and give the same effect as headlights....at a somewhat lower intensity. In fact, I asked a Virginia State Trooper about that, because, at first, I found the law somewhat confusing, too.
Lexus Champion
Joined: Aug 2006
Posts: 12,525
Likes: 266
From: Illinois
I have an A6 and the LED DRL's are pretty bight. I can see that it might reduce the effectiveness of the turn indicators if they remained on. On my car one of the two white led strips flashes amber when the DRL switches off and it looks like most of the DRL has switched to amber.