Neotraditional streets vs. segragated streets in terms of traffic safety

[Samminn]

Hi everybody.

I'm new to this, what appears to be, an excellent community. Glad to join.

I'm, together with my superior here at my bureau, developing and applying for a research project which intends to determine if a neotraditional street network (pre-segregated network) with modern traffic calming remedies, can achieve the same level of traffic safety as the suburban style segregated system.

In other words answering this question: "can we apply neotraditional urban planning from the currently prevalent segregated systems planning without comprising traffic safety?"

Do you know of similar studies from elsewhere? Or can you give me advice on how to find international sources for a project such as this?

With thanks in advance
Samuel T. Petursson
Reykjavik Iceland.

[DetroitPlanner]

In other words answering this question: "can we apply neotraditional urban planning from the currently prevalent segregated systems planning without comprising traffic safety?"

Three lanes roads often move more traffic four lane roads and are a lot safer.
On street parking provides a safe buffer between the motorist and the pedestrian (though bicyclists have to be wary of folks opening up car doors on them (this happened to my sister a few times, people are stupid).
Landscaped Blvds are safe.
Roundabouts are seen as a way to reduce both the number and severity of crashes at an intersection.
Speed laws need to be enforced.

These recommendations do not translate well to every situation. For example, a three laned freeway would be chaos. Most planners would need to work with police and fire to ensure that enough access is allowed to reach all properties in the event of a fire.

Look at how older cities were developed with the auto in mind, places like Detroit are very similar in nature to neo-traditional communities (mostly single family, with some flats, apartments and retail along the major corridors). Be open that no matter what you do, people are still going to get in their cars and drive to Super K-martif it makes economic sense to do so.

[chukky]

For example, a three laned freeway would be chaos.

.

Hmmm.Brisneyland has a fair few three laned freeways around and about - they seem to work ... whats inherently evil about them?

[Samminn]

How are regulations in the US or Australia? Are they very strict on how you define every street according to the well known 4 types of roads: arterial road, connecting road, collecting road and access roads (if I remember it correctly)?

Are there no big obstacles to designing large new urban areas where you apply neotraditional principles, such as on-street parking along central boulevards, short intervals between intersections and so on?

[DetroitPlanner]

Hmmm.Brisneyland has a fair few three laned freeways around and about - they seem to work ... whats inherently evil about them?

Do you mean three lanes in each direction? I mean three lanes period, no barrier walls. Left turns off of freeway onto ramps.

[chukky]

Do you mean three lanes in each direction? I mean three lanes period, no barrier walls. Left turns off of freeway onto ramps.

ah, i see, with you now.

[ABS]

Here are the official engineering requirements for roads within the Brisbane City Council local government area:


Minor and Industrial Roads (128kb) PDF Format

Major Roads (219kb) PDF Format

Draft Water Sensitive Urban Design Minor Roads (249kb) PDF Format

[Samminn]

Thanks ABS.

This will come in handy.

Cheers
Samminn

Anyone else?

[ABS]

Have a look in the Resource Directory of this website (Cyburbia) and you should find a few very good links to road and roundabout design sites.

[Transport Queen]

Good resource on when to use what street types.

http://www.wapc.wa.gov/Publications/27.aspx

Cheers!
TQ

[ABS]

http://www.wapc.wa.gov.au/Publications/27.aspx

Fixed the dead link

[ssnyderjr]

Three lanes roads often move more traffic four lane roads and are a lot safer.

This is only true where there are many, many driveways, and there is a threshold of about 20k ADT for 3 lane roads to work. We have a road that sees about 20-22k AADT and a 3 lane simply would NOT work, it would be backed up a long way, and you could not access it (turn into it) for 5-10 minutes at a time during peak hours.

The cities of Angola, In, and Bucyrus, OH tried this (converted a 4 lane into a 3 lane) on state routes and both are backed up horribly during peak times (and Angola's is backed up constantly. The Level of Service (LOS) for these intersections has to be D at BEST.

I do agree that many 4 lanes can be turned into 3-lanes without compromising much. That was due to overdesign of engineers in the past. I also agree, that at times a 4-lane is cumbersome, requiring several lane changes, but overall it is still a more efficient road in general.

[jmello]

I do agree that many 4 lanes can be turned into 3-lanes without compromising much. That was due to overdesign of engineers in the past. I also agree, that at times a 4-lane is cumbersome, requiring several lane changes, but overall it is still a more efficient road in general.

I personally cannot stand suicide lanes (center turning lanes), from a safety, aesthetic and walkability POV. I was surprised to see them so prevalent in North Carolina, even on inner-city arteries.

I would much rather see landscaped medians. However, Rhode Island DOT introduced a center lane paved with brick in Barrington, RI (one of Money's best cities) and it seems to work from both an aesthetic and safety standpoint.

[nuovorecord]

Here are a few resources that may assist you:

Iowa DOT Study on reducing from 4 to 3 lanes

Oregon publications on street design

A collection of reports for the Surface Transportation Policy Project

Michael Ronkin and Dan Burden are internationally recognized experts on safe design of streets for peds/bikes and cars.

Finally, you should check out the work Hans Monderman is doing in The Netherlands and elsewhere.

Hope these help...good luck!

[abrowne]

Hi everybody.

I'm, together with my superior here at my bureau, developing and applying for a research project which intends to determine if a neotraditional street network (pre-segregated network) with modern traffic calming remedies, can achieve the same level of traffic safety as the suburban style segregated system.

From what I understand, neotraditional thought dictates that traffic calming consists of two simple things: narrower streets, and parallel parking.

[JohnHupp]

This is only true where there are many, many driveways, and there is a threshold of about 20k ADT for 3 lane roads to work. We have a road that sees about 20-22k AADT and a 3 lane simply would NOT work, it would be backed up a long way, and you could not access it (turn into it) for 5-10 minutes at a time during peak hours.

Three-lane roads are often more ideal replacements for two-lane roads than for four-lane roads. The third lane is especially useful when a road needs to sustain moving traffic and suffers from backups created by people making left turns. In some areas, however, a third lane would be useless, due to a lack of driveways; alternately, the traffic volume may dictate the necessity of a four-lane road.

[JohnHupp]

On street parking provides a safe buffer between the motorist and the pedestrian (though bicyclists have to be wary of folks opening up car doors on them (this happened to my sister a few times, people are stupid).

Perhaps diagonal parking could alleviate the issue of doors while increasing the parking capacity of a road.

Landscaped Blvds are safe.

A median can provide pedestrians with a sort of oasis when crossing the street. The division can also protect drivers from oncoming traffic. And maybe the narrower appearance of a treed boulevard subconsciously makes people drive more slowly.

Roundabouts are seen as a way to reduce both the number and severity of crashes at an intersection.

Roundabouts can be very efficient, but they are rarely used, at least in Chicago. I have seen them used mostly as a way to make drivers slow down in residential areas. The problem that arises when they are used on a larger scale is that Americans don't seem to know how to use them. In Australia I have seen many roundabouts joining four-lane roads; in Chicago the only such roundabout I've seen is chaos (though it does in fact have five, not four, points). But if they become part of our cultural driving vocabulary, roundabouts could be extremely useful.

Speed laws need to be enforced.

Automatic speed and red-light cameras are wonderful things. Imagine that if they fined every violator, they could afford to put in more cameras, and by the time they were everywhere, speeding would have severely tapered off. (Automatic traffic-control devices, from "smart" stoplights to RFID toll collection, seem to make everything run more smoothly.)

[ssnyderjr]

From what I understand, neotraditional thought dictates that traffic calming consists of two simple things: narrower streets, and parallel parking.

But sucks for street sweeping/snow plowing if you must contend with those two animals.

[Samminn]

Here are a few resources that may assist you:

Iowa DOT Study on reducing from 4 to 3 lanes

Oregon publications on street design

A collection of reports for the Surface Transportation Policy Project

Michael Ronkin and Dan Burden are internationally recognized experts on safe design of streets for peds/bikes and cars.

Finally, you should check out the work Hans Monderman is doing in The Netherlands and elsewhere.

Hope these help...good luck!

Thanks a lot. This will definately help!

Good question abrowne on the concept of neotraditional street planning and its principles. The project that me and my colleagues are preparing for will focus on analysing traffic safety in two neighbourhoods. One that was developed and constructed in the pre-auto age, with only a rather vague segragation of streets into arteries, connectors, collectors and residential streets. No Cul-de-sacs and a lot of parallel parking. The other one is a typical post-autoage neighbourhood, with segragated system, pedestrians segragated from autos and no parallel parking allowed.

There is a widespread interest here in Iceland, as well as in the rest of Scandinavia and northern Europe, to break down as many barriers to designing new high-density neighbourhoods with the same sort of blending and mixing that characterizes pre-autoage districts. All in the name of a sense of community, livability, variety, thriving culture and sustainability in general. One barrier is the current viewpoint that traffic safety cannot be maximised unless segregation principles are applied. We want to examine that barrier and try to determine whether measures such as traffic calming and raised intersections can reach the same degree of traffic safety.

[noj]

Samminn,

Although (as you allude to), the issue of transport throughput in high desnity neighbourhoods is quite a big issue in the UK, unfortunately I don't have enough detailed knowledge to point you in the direction of any relevant research.

However, the following links may prove useful:

PP3: Housing

Better Places By Design - A Companion Guide to PPG3

They are both links to guidance published by the UK government, and the companion guide in partiucular has interesting sections on downgrading highways and slowing traffic to make a community more walkable and liveable.

The guidance is being taken on well here; after the usual initial reticence from Highways Engineers they are amost being forced down the route now!

Good luck.

[boiker]

Our PW department knows of two roads:

under 10k ADT and over 10k ADT

under 10k ADT = 2 lane often with protected left turns sometimes protected rights
over 10k ADT = 4 lane w/ center suicide lane, often w/ protected rights and lefts at major intersections.

I discussed this with the traffic engineer. He, rightly, claimed that once a road is over 10k a day, IDOT standards are for the road to be 4-lane. The PW dept likes to mirror the state's standards. We are in the process of converting a stretch of road that has an ADT of 10-15k from 2-lane to 4 lane w/ shared center turn lane.

[Transport Queen]

But sucks for street sweeping/snow plowing if you must contend with those two animals.

In places with a lot of snow, where there is onstreet parking, I think the streets are signed for no parking in the evenings or some period during the day when plows can get there.

[Margin Walker]

Our PW department knows of two roads:

under 10k ADT and over 10k ADT

under 10k ADT = 2 lane often with protected left turns sometimes protected rights
over 10k ADT = 4 lane w/ center suicide lane, often w/ protected rights and lefts at major intersections.

I discussed this with the traffic engineer. He, rightly, claimed that once a road is over 10k a day, IDOT standards are for the road to be 4-lane. The PW dept likes to mirror the state's standards. We are in the process of converting a stretch of road that has an ADT of 10-15k from 2-lane to 4 lane w/ shared center turn lane.

Wow! Seems like IDOT standards are a bit over the top. A two lane road should be able to handle 20k vehicles/day (at least) and more if you have separate left and right turn lanes. We have some two lane roads here that are performing adequately (for the moment) with close to 30k vehicles per day on them. Not that we wouldn't upgrade them given the opportunity

[The One]

Go with the small cross sections and the highest level of finish possible for pedestrian access in your urban core areas. In the rural areas, stick to better vehicle support, since your vehicle can be the difference between life and death in your climate at certain times of the year. Forget about our 1960's road classification system and go with your more Europeanized version, YOU WILL NOT REGRET doing so!

The answer to your question is YES! If your version of segregated roadway systems is anything like ours in the states, then you have massive pedestrian & bicycle conflicts everywhere and your crosswalk system is similar to a game of Russian Roullette, the one with 6 out of 6 bullets!! (and yes, its a revolver )

With such a low population density, I'm not sure why you would need to make "American" style changes??? From what I saw on the Amazing Race (about the only real overseas travel I get to do nowadays ), your street systems look good, with a lot of roundabouts and narrow pedestrian crossings My advice is don't try to change what may be a good system.....

[ssnyderjr]

Our PW department knows of two roads:

under 10k ADT and over 10k ADT

under 10k ADT = 2 lane often with protected left turns sometimes protected rights
over 10k ADT = 4 lane w/ center suicide lane, often w/ protected rights and lefts at major intersections.

I discussed this with the traffic engineer. He, rightly, claimed that once a road is over 10k a day, IDOT standards are for the road to be 4-lane. The PW dept likes to mirror the state's standards. We are in the process of converting a stretch of road that has an ADT of 10-15k from 2-lane to 4 lane w/ shared center turn lane.

Why not go from 2 lane to 3 lanes, w/suicide lane?? Don't understand the rationalle behind going from 2 to 4 (er 5 counting the suicide). Just seems like alot of overdesign (unless you project traffic otherwise), because a 3 lane serves 15k very well in most instances, depending on # of driveways. We have a few 2 lane, and several 3 lane arterials (state routes) that take 10-15k+ very well and is not horribly congested. I still don't think you are getting into that 4 or 5 lane need until over 20,000. That is the first time I have heard a threshold like that for a state. Thanks for the info.