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defining street types by ADT

SGB

Cyburbian
Messages
3,388
Points
26
I'm working with one of our communities on updating their subdivision regulations. Currently, they define street types as follows:
  1. Arterial streets and highways are those used primarily for fast or heavy traffic.
  2. Collector streets are those which carry traffic from minor streets to the major system of arterial streets and highways. Collectors may also serve as secondary arteries to carry some through traffic.
  3. Local streets are those which are used primarily for access to the abutting properties.
  4. Marginal access streets are minor streets which are parallel to and adjacent to arterial streets and highways and which provide access to abutting properties and protection from through traffic.
I'd like to recommend changing these definitions so that street types are described by average daily traffic (ADT).
Does anyone have some model suggestions? And no, our office does not have any edition of the ITE bible. Sigh....
 

NHPlanner

A shadow of my former self
Staff member
Moderator
Messages
9,945
Points
40
Our ordinance has the following (and it's probably nothing like you're looking for):

Arterial - A road intended to carry local and regional traffic to, from and between limited access highways as well as to, from and between the major centers of employment, service, and retailing in commercial and industrial districts. These rads are designed to carry large volumes of traffic to and from collector streets. The emphasis is on mobility, not access to adjoining land uses. Arterial roads are characterized by high volumes of traffic and two to four travel lanes.

Collector - A road intended to carry local vehicular traffic within commercial and industrial districts as well as to, from, and through residential areas to reach arterial streets and the commercial and industrial districts. Collectors provide access to adjoining land uses, as well as conduct traffic from local streets to arterial streets and interstate highways. Collector roads are characterized by high volumes of traffic at peak hours and two (2) travel lanes, often with additional turning lanes at intersections.
 

JNL

Cyburbian
Messages
2,449
Points
25
I did a quick search and found a 2001 paper comparing 'Road classification systems - Christchurch and Toronto'. (=Christchurch, New Zealand). It critiques their ADT-based road hierarchies. It's a PDF file, 18pp. Let me know if you'd like me to send it to you :)
 

Wulf9

Member
Messages
923
Points
22
What's the purpose of the definition? If you are planning for traffic (e.g. carry traffic on arterials, don't let collectors become quasi arterials, and assure peace and quiet on neighborhood streets) you need one thing. If you want to determine how wide to make the streets based on current or expected ADT, that's another thing.

The peace and quiet standards for residential areas are best done with a "lower than capacity" ADT. A neighborhood street usually has capacity for thousands of trips, but it is not a true neighborhood street unless trips are in the hundreds.

It is also worthwhile to look at the amount of new traffic that causes one to think traffic increase is noticeable (the ADT is 5,000 trips. The existing traffic is 500 trips. An increase of 50 trips will seem large even thought the street is way below "capacity.") Increases of 10% of existing traffic are usually noticeable. Increases less than 10% are usually not noticed. This info is from a study many moons ago, but it still seems valid.
 

Tranplanner

maudit anglais
Messages
7,916
Points
36
JNL said:
I did a quick search and found a 2001 paper comparing 'Road classification systems - Christchurch and Toronto'. (=Christchurch, New Zealand). It critiques their ADT-based road hierarchies. It's a PDF file, 18pp. Let me know if you'd like me to send it to you :)
Okay - maybe I should hold off digging up our AADT-based road hierarchies. In Toronto's case, they are suggested levels used to determine if a roadway is performing its intended function and if any changes are required (e.g. traffic calming).
 
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