What's the rationale for a doghouse signal here?

[1995hoo]

In the picture below, I was waiting at the light going from Jeff Todd Way to Mount Vernon Memorial Highway (VA-235) at the intersection with US-1 just outside Fort Belvoir in Virginia. Google Maps' depiction of the intersection is outdated–it's a straight-up crossroads–and the Street View is outdated since Jeff Todd Way is a new road that opened late last year. In the direction I was going, there are four lanes: Two left-turn-only lanes to northbound Route 1, a single straight-ahead lane (the one I was in when I took this picture), and a single right-turn lane to southbound Route 1.

Note there are four signals corresponding to the four lanes. So what's the point of putting up the doghouse signal for the right-turn lane? That lane could, of course, have a turn arrow when the other three lanes all have red lights, but why have a doghouse for that purpose when that lane is always a turn-only lane?





Edited to add: This is not the only time I've seen this sort of thing, but I was bored sitting there at the red light and it simply occurred to me that this signal configuration doesn't really seem necessary.

[Big John]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

[Brandon]

In Illinois, it would be so that the right turn lane could have a green arrow for a protected movement when the left turn signals have green arrows (protected) are on for the crossroad.  When the crossroad left turns yellow, so does the right turn.  And why a tower (we use towers in stead of doghouses)?  IDOT requires a minimum of three signals for the through movement, and two signals for each turning movement.  Thus, here, there would be a nearside tower signal.

[spooky]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

*ding ding ding* we have a winner.

[1995hoo]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

[mrsman]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

[Brandon]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

And like I said, some states go beyond that even (see my post regarding Illinois above).

[froggie]

A combination of Big John and Brandon's responses.

While VDOT has gone away from its former one-signal-per-lane requirement, it still generally follows it in practice.  But as Big John noted, you need at least two signals for the through movement (for good reasons like what mrsman mentioned), and there's only a single through lane here.

[jakeroot]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

I don't mind more signals than necessary (I've always been a big proponent of side-mounted signal repeaters) but given that most new signals are LEDs, should this requirement still be ... a requirement?

[jeffandnicole]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

I don't mind more signals than necessary (I've always been a big proponent of side-mounted signal repeaters) but given that most new signals are LEDs, should this requirement still be ... a requirement?

Yes. LEDs may not burn out like traditional bulbs, but they still will burn out or fail on occasion.

[jakeroot]

I think it was done that way to satisfy the MUTCD requirement of 2 primary signals for the through movement.

Ah, thanks. Wasn't aware of that requirement. Seems like a waste in many cases, but as the government types say, "If that's what the book says...."

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

I don't mind more signals than necessary (I've always been a big proponent of side-mounted signal repeaters) but given that most new signals are LEDs, should this requirement still be ... a requirement?

Yes. LEDs may not burn out like traditional bulbs, but they still will burn out or fail on occasion.

Isn't it more likely that a single LED will fail rather than the whole array? Not saying catastrophic failure is impossible, just incredibly unlikely.

(I suppose as long as it's possible, the rule should continue to exist -- I'm just discussing this for the sake of discussing it).

[roadfro]

2 signals is not a waste.  I believe it's a requirement to deal with a situation where a signal light bulb may be burned out.  At least you have a second signal until the light bulb can be replaced.

I don't mind more signals than necessary (I've always been a big proponent of side-mounted signal repeaters) but given that most new signals are LEDs, should this requirement still be ... a requirement?

Yes. LEDs may not burn out like traditional bulbs, but they still will burn out or fail on occasion.

Isn't it more likely that a single LED will fail rather than the whole array? Not saying catastrophic failure is impossible, just incredibly unlikely.

(I suppose as long as it's possible, the rule should continue to exist -- I'm just discussing this for the sake of discussing it).

More often, what I've seen is that a section of the LEDs will fail at once, not usually a single LED. For example, older LED bulbs arranged in rows (as opposed to newer LEDs in a circular/radial pattern) it can be a row or two of individual bulbs a couple inches wide. This seems to be a failure of the technology rather than an individual LED light element failing. Some LEDs get gradually dimmer in lieu of going blank suddenly.

[Scott5114]

Most new signals are LEDs, but not all. (I'm pretty sure ODOT is still putting up incandescents, even though none of the cities around here do...)