Municipal Class Environmental Assessment

Part B - Municipal Road Projects

B.2.3 INTERCHANGES, GRADE SEPARATIONS AND WATER CROSSINGS

B.2.3.1 Description of the Projects

Projects in this group can generally be described as:

 

B.2.3.2 Purpose of the Project

The requirement for an interchange will generally arise because of high existing or anticipated turning movements relative to the carrying capacity of an existing intersection or interchange. An interchange provides a significant-means of improving capacity by increasing the ability to handle turning movements and thereby reducing conflict between through and turning traffic. Collision experience and system compatibility may also contribute to the justification for an interchange.

A grade separation is generally justified where high existing or anticipated traffic volumes are identified. Reference to traffic in grade separation projects developed under this Class EA will generally mean road traffic although rail traffic may also justify the need for grade separation. A combination of high road traffic and high volume/high speed rail traffic will give rise for the need for a grade separation. A grade separation will be the preferred solution when turning movements are generally low or can be relocated. Similarly, a grade separation will be justified where high collision experience is a major factor.

A water crossing will be justified where an existing or a new roadway is required to cross a river, lake, canal, bay or similar water body. Replacement or modification to an existing water crossing facility may be necessary to address a structural deficiency, a functional deficiency related to transportation demands or a functional deficiency related to hydrological conditions.

 

B.2.3.3 Alternative Solutions

Interchanges:

a) Existing At-grade Intersection:

Where a deficiency is identified at an existing at-grade intersection the following alternative solutions may be considered:

  1. minor reconstruction, e.g. add right or left turning lanes.
  2. modify existing facility through non-structural improvements such as signing or traffic controls.
  3. modify grade and/or alignment and/or cross-section.
  4. provide a grade separation.
  5. divert traffic.
  6. resolve a deficiency elsewhere in the road network.
  7. “do nothing”.

b) Existing Interchange:

Where a capacity deficiency is identified at an existing interchange, the alternative solutions which may be considered would include the alternatives considered above for existing at-grade intersections together with the following:

  1. add an interchange elsewhere in the road network.
  2. modify or replace the existing interchange.

c) No Existing Intersection or Interchange:

Where a new interchange is necessary and no intersection or interchange currently exists, all the alternative solutions listed above may be considered.

Grade Separations:

a) Existing At-Grade Intersection:

Where a deficiency is identified at an existing at-grade road/rail intersection, the following alternative solutions may be considered:

i)       modify the existing facility through non-structural improvements such as signing, traffic signals, wigwams, railway gates. 

  1. modify grade and/or alignment and/or cross-section.
  2. provide a grade separation.
  3. iv) “do nothing”.

b) An Existing Grade Separation: Road/Rail or Road/Road:

At an existing grade separation the following alternative solutions may be considered:

  1. increase width over the grade separation.
  2. increase width under the grade separation.
  3. modify grade separation to an interchange.
  4. “do nothing”.

c) Water Crossings:

Where a water crossing is necessary for a new roadway, there are very few practical alternatives to the water crossing which can be considered. In exceptional circumstances, where the water body is of such width or has such navigational requirements, a tunnel or a surface water transportation system, such as a ferry, might be considered as alternatives.

A transportation deficiency specific to a water crossing site may require the replacement or modification of the existing roadway water crossing or the construction of a new roadway water crossing. Alternative solutions which may be considered are:

Road Deficiencies:

  1. modify the existing facility through non-structural improvements such as signing or traffic controls
  2. divert traffic to other existing roads and/or water crossings
  3. resolve a deficiency elsewhere in the road network
  4. restrictive traffic signing or closure of the road
  5. reconstruct the water crossing
  6. “do nothing”

Hydraulic Deficiencies:

  1. increase hydraulic capacity
  2. “do nothing”