Laurelwood and Erbsville

Twitter! Wow a new source for constituent concerns. But not all answers are 140 characters long. Usually I speak to people by phone or e-mail (almost never get a written letter) but since the issue of an advance green arrow at Laurelwood and Erbsville is public on twitter, I will answer on my blog. Ah, the modern world!

A regualr reader found staff’s reply confusing. Oh that engineer language! I will try to make it clear by bolding relevant points.

We are talking about what is called a left turn arrow where a green arrow on the traffic light allows cars to turn left while the opposing traffic and traffic on the left and right still have a red and are stopped. Otherwise, cars are unable to turn left.

Here is staff’s reply:

Jane, 

I will have staff look into the advanced left-turn at Laurelwood.  It should be noted that our research suggests that additional left-turn phasing does not improve safety at intersections and can actually increase the number of collisions.  Therefore we do not be consider this suggestion to be a collision countermeasure.  Adding a left-turn phase also takes time away from the pedestrian walk interval; a disadvantage to the pedestrian.  Alternatively,  fully protected left-turn phasing (when left turning motorists are permitted to turn left on an exclusive green arrow only) is considered a collision countermeasure (reduces accidents), however this proven collision countermeasure has greater impacts to delay for all users of an intersection.  

Additionally, when you add a left-turn phase, it takes time away from the opposing traffic, as well as other movements, thus resulting in fewer gaps in opposing traffic for the remaining left-turning motorists.  More importantly, our most common type of pedestrian collision involves left-turn vehicles searching for gaps in opposing traffic, committing to their turn and striking pedestrians leaving the curb. 

For these reasons, we only install protected/permissive left-turn phasing when it is required for capacity / demand reasons.

Jane again. I have contacted Waterloo Police to check out the kids crossing against the light.

Advertisements

One response to “Laurelwood and Erbsville

  1. A quick note – opposing (southbound) traffic is minimal; the majority of SJAM’s catchment area, and the related traffic come from south of the school. There was a letter to the editor in the Record blaming tie-ups on Erbsville on the roundabout (false, in my opinion). The traffic jams are north of the roundabout, and likely because of the signalized intersections. Thanks for looking into this.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s