Max # of Dwelling Units on Dead-end Streets

[Seabishop]

What do planners out there think is a good maximum number of dwelling units allowed on a dead end street and why? This question assumes adequate public water and sewer. I know fire dept. input is important here but I just wanted to see if your communities have thought this one out. Our regs allow up to 600' feet without mention of density. There are several dead-ends both new and old that are far beyond 600'.

 

[NHPlanner]

We don't have a density requirement. We have a minimum and maximum length in our regs (450' min, 1200' max). I believe the max was based on Fire Department input on length of hose capabilities.

The minimum was established to prevent "lollypops or bulbs" for the sole purpose of creating frontage to cram in more lots.

 

[Tranplanner]

I'm not sure why you would want to limit the number of units/density on a cul-de-sac - can you explain a bit more?

I think our fire department limits "dead-end" streets to 90m in length, without a turning facility. Not sure if there is a maximum length if a turnaround facility is provided.

 

[Seabishop]

I'm not sure why you would want to limit the number of units/density on a cul-de-sac - can you explain a bit more?

Depending on the zone and lot sizes 600' can get you up to about 10 single family units or 50 multi-family units. Too many units with only one point of access has been a concern before and I'm not sure length alone covers it. The old argument is if a fallen tree blocks the street emergency vehicles can't make it in. Traffic onto the collector road can also be a concern.

I'm also not sure how we ended up with 600' as a limit years ago but that's another question.

 

[Plannerbabs]

We limit them to 650' from the intersection of centerlines to the radius of the bulb. The main concern, as I understand it, is safety. Unfortunately, the bulbs tend to become parking lots for cars, bicycles, etc over time, which can limit access. The other argument is that closed-end streets are safer for children, to which one replies, "Don't let your kids play in the street." Not that that can be regulated. ;-)

 

[Rem]

We don't have a length requirement but currently require:

Where culs-de-sac/dead end streets are incorporated into road design:

• The end of the cul-de-sac should be clearly visible from the cross street.
• On-road parking bays are provided within the head of the cul-de-sac.
• The cul-de-sac is designed as a T-head or Y-head. Circular cul-de-sac heads are discouraged as they do not optimise orderly lot layout, solar access or energy efficiency.

Note - The use of culs-de-sac should be kept to a minimum. A modified grid road network is preferred.

This is a relatively new provision - we used to permit up to 60 dwelling lots per dead end street (say 30x20 metres, 600 metres long or nearly 2000 feet) but they were hopeless and even the developers didn't use this sort of length. Applying connectivity principles, the above controls are now being used.

If you would like to look at the controls in more detail try this link, go to DCP No. 1, Download F.

 

[jordanb]

Couldn't the firetrucks just back up?

 

[Lee Nellis]

In rural areas where longer cul-de-sacs can make sense from several perspectives, I do limit the number of homes served. The client obviously gets involved in setting the number, but the ordinances I have done allowed from 16-24. Is there "science" behind that? No. Just an informal assessment of how much risk one wants to take. I agree that 50 homes is too many on a cul-de-sac. The 24 is uncomfortable, but not very. 16 is the number I picked after thinking it through.

 

[Seabishop]

Couldn't the firetrucks just back up?

Planners have been asking this question for years. :-D And the larger the firetrucks get the larger the cul-de-sac radii get.

 

[nerudite]

My understanding on one of the reasons why they limit the size of dead ends is due to emergency access. If you think about it, if you have 60 lots on a street with only one access, and that access is blocked, how do you get the fire trucks in? The longer the cul-de-sac with no other outlet, the more people that may be affected if something happens in that street. The way we deal with it here (and in Davis when I was there) was connect cul-de-sacs with walking trails that double as emergency access points. So in case of an emergency and the street is blocked, you can still get to it from another street.

Also, the longer the street, the worse the water pressure if it isn't in a looped system...

And finally... long, straight cul-de-sacs make for ugly streetscapes.