3.0 Streets and Transportation Design

Question 1

Lane width

Answer 1

• Design consistency is a factor in traffic safety
• Avoid large variations
• If there is extra width, the pedestrian space, boulevard, or the tree median should be widened rather than widening the travel lanes
• The lane width on curves should have an additional minimum of 0.2m width on both sides
• Use compound curves: wider lane through the curve into a straight segment

Question 2

Horizontal design

Answer 2

• Should follow TAC Geometric Design Guide for Canadian Roads
• All curves should have a minimum 20m tangent between any road intersection and the curve
• S curves must have 20m tangent separating the two curves

Question 3

Right-Angle Curves

Answer 3

• For local residential roads
• The radius is larger than 9.0 m

Question 4

Vertical Design

Answer 4

• Should follow TAC Geometric Design Guide for Canadian Roads
• It may be omitted where the algebraic difference in grades does not exceed 2% for local roads and 1% for other streets
• The minimum longitudinal grade shall be 0.5% for drainage

Question 5

Max Longitudinal grades

Answer 5

Different every city

Question 6

Cross Fall

Answer 6

• 2.5% is standard
• Variations to this may be permitted

Question 7

Horizontal and Vertical Clearance

Answer 7

When vertical clearance requirements are not met, low clearance signs are to be installed

Question 8

Intersection Design

Answer 8

• Shall be designed at right angles or as close as possible (70-110 degrees)
• A min. 20m tangent at all intersection approaches
• Intersections proposed on curves or near the crest of hills are to be avoided as much as possible
• Sightline analysis with TAC
• Profiles on the approach to an intersection should be flattened for a min. Distance of 20m back
• When signals exist, cross slopes through streets are to be reduced between 0.5-1.5% within the intersection
• Minor roadway profile changed to fit the crown of major roadway or opposite

Question 9

Curb Return treatment

Answer 9

The radius of the curb face

Question 10

Right Turn channelization islands

Answer 10

• Should be avoided where possible (sight line, speed)
• A two-centred compound radius curb return may be required in conjunction with the raised island for the design vehicle (for pedestrian and accessibility)