The service road that exists parallel to Highway 2A between 54th Avenue and 63rd Avenue (Airport Road) operates as a frontage road to provide direct access to a number of highway commercial businesses along this stretch of highway. As the traffic volumes increase on the highway as well as the local street system as Lacombe grows it will be critical that the access points to this service road at 45th Street, Woodland Drive, Dicken’s Lane and 63rd Avenue continue to provide function safely while providing the necessary accessibility to the businesses.
If not managed well, the access points of a frontage road to the highway and local road network can become collision prone locations as there is minimal separation between the edge of the highway and the frontage road intersection. Given the volume of traffic that accesses the highway commercial land uses along the frontage road as well as the local traffic traveling through on the local road network, there are a significant amount of conflicts that occur in a relatively small area. In order to manage the trade off between accessibility and the mobility demands while maintaining a reasonable level of safety performance, research on these locations has shown that certain configurations only operate well to certain traffic volume levels.
The Geometric Design Guide for Canadian Roads by the Transportation Association of Canada suggests volume thresholds for Frontage Road design. These were discussed previously in this report and are repeated here for clarity:
Type 1: Cross Road Volumes less than 2000 vehicles/day - Unsignalized
Highway Intersection
The frontage road operates with all movements to/from the cross road.
A minimum 24 metre separation between the edge of the through lanes of
the highway and the frontage road is required to allow a single unit truck to
make the turn from the highway to the frontage road.
Type 2: Cross Road Volumes greater than 2000 vehicles/day – Signalized Highway Intersection
A minimum 24 metre separation between the edge of the through lanes of the highway and the frontage road is required to allow a single unit truck to make the turn from the highway to the frontage road. The short distance between the highway and the frontage road intersection cannot accommodate higher traffic volumes without unacceptably increasing collisions. As a result, it is recommended that the frontage road intersection be restricted to right in and right by a raised median down the centerline of the cross road when the cross road volumes exceed 2000 vehicles/day.
Type 3: Cross Road volumes greater than 5000 vehicles/day – Signalized Highway Intersection
A minimum 45 metre separation between the edge of the through lanes of the highway and the frontage road is required to allow all movement between the frontage road and the cross road with cross road volumes in excess of 5000 vehicles/day. The frontage road intersection can be signalized if warranted, but it will need to be coordinated with the signal at the adjacent highway intersection.
Note that in all cases, the safety performance of this intersection should be monitored. If the collision frequency rises to an unacceptable level, consideration should be given to implementing the improvements recommended here in advance of the traffic volumes reaching the stated threshold volumes.
63rd
Avenue
As development occurs in the northern area of Lacombe, the traffic volumes will increase on 63rd Avenue and will exceed the 2000 vehicles/day threshold of the Type 1 configuration and for a period of time will be less than the 5000 vehicle/day requirement of the Type 3 configuration. During this interim period all turning movements from the Service Road will continue to be approximately 24 metres away from the Highway. At this point the service road intersection should be upgraded to Type II with the current offset from Highway 2A retained, and a median be installed that restricts the Service Road to right in/out.
Once the 5000 vehicle per day threshold is reached, the service road intersection should be moved to a 45 metre separation from the highway and all movements be maintained as per the Type 3 configuration. The Type 3 configuration is recommended as it anticipates the future higher traffic volumes on 63rd Avenue and provides at access to the Service Road from the north on Highway 2A. Right Of Way is required form the parcels of land on the southwest quadrant of the Service Road/63rd Avenue intersection to accommodate the 45 metre separation between the Highway and the Service Road for a Type 3 configuration.
Concurrent with the improvement to Type III are the following geometric improvements:
· Construct a southbound to westbound right turn lane from Highway 2A. This is an interim measure which will prolong the length of time that the Service Road intersection can function as all movement intersection without relocating the Service Road from 24 m to 45 m from the highway alignment. A right turn island with a yield sign is required in this configuration to ensure that the right turning traffic from Highway 2A will yield to traffic already on 63rd Avenue which is waiting to turn left from westbound 63rd Avenue to southbound on the Service Road.
· The westbound width of 63rd Avenue between Highway 2A and the Service Road should provide at least 8.0 m of pavement to allow a vehicle to go around another vehicle that is waiting to turn left onto the southbound Service Road. The road should be marked as 4.5 m lane with a wide shoulder. If the pavement is not widened, through vehicles will be caught behind a turning vehicle and may queue back onto the highway through lanes.
The geometric design for this intersection is
illustrated in Exhibit
8-7A.
The projected volumes of Dicken’s Lane at the Highway 2A intersection for the 20,000 population horizon will exceed 2000 vehicles per day and the Highway 2A intersection is not predicted to require a traffic signal by that time. This intersection is currently a Type 1 intersection, but does not clearly fall into one of the categories described by TAC for the 20,000 population level. As such, it is recommended that:
· A southbound to westbound right turn lane from Highway 2A be constructed to prolong the length of time that the Service Road intersection can function as all movement intersection. A right turn island with a yield sign is required in this configuration to ensure that the right turning traffic from Highway 2A will yield to traffic already on Dicken’s Lane which is waiting to turn left from westbound Dicken’s Lane to southbound on the Service Road.
· The westbound width of Dicken’s Lane between Highway 2A and the Service Road should provide at least 8.0 metres of pavement to allow a vehicle to go around another vehicle that is waiting to turn left onto the southbound Service Road. The road should be marked as 4.5 m lane with a wide shoulder. If the pavement is not widened, through vehicles will be caught behind a turning vehicle and may queue back onto the highway through lanes.
The geometric requirement for the Dicken’s Lane
intersection is illustrated on Exhibit
8-7B.
Woodland
Drive
The west side intersection with the service road is currently organized as a Type I intersection, carrying a daily volume of less than 2000 vehicles per day. As noted previously in this report, this intersection can be allowed to continue to function in the existing configuration until such time as daily volumes exceed 2000 vehicles per day, as which time the intersection would normally be upgraded to a Type II design with a median restricting movements to right turns only. However, given (a) the strategic placement of this intersection in the midpoint of the Highway 2A service road, and (b) the long term forecasts of 5000 to 7000 vehicles per day on Woodland Drive at this location, it is recommended that the intersection be upgraded to Type 3 with a 45 metre separation once daily traffic volumes exceed 2000 vehicles per day.
The Type 3 configuration is recommended as it anticipates the future higher traffic volumes on Woodland Drive and provides at least a single full movement access at a point mid way along the Service Road. Right Of Way is required from the parcels of land on the northwest and southwest quadrants of the Service Road/Woodlands Drive intersection to accommodate the 45 metre separation between the highway and the Service Road for a Type 3 configuration.
The recommended design is illustrated on Exhibit 8-7C.
Assuming that the geometric improvements noted in the short term recommendations have been incorporated into this intersection before the 20,000 population horizon, no further geometric improvements will be necessary.
Signalization may be required at one of these two locations by the 20,000 population horizon, and either location could be selected as the candidate intersection, though signalization of both intersections is not recommended. Note that the direct connection of 54th Avenue to Highway 2A at this location is not recommended as it would compromise the operation of the service road.
The organization of the road network in this area, including Heritage Way, 45th Street, 54th Avenue and Highway 2A is shown conceptually on Exhibit 8-5.