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 become critical that the access points to this service road at Heritage Way, 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 the following volume thresholds for Frontage Roads:
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.
The issues at the Woodland Drive intersection were discussed in the previous section as part of the upgrades recommended at the Woodland Drive/Highway 2A/Wolf Creek Drive intersection. As such, Woodland Drive will not be included here as part of the discussion of the service road intersection improvements.
It is noted that although some of the service road intersections clearly require upgrading today under existing traffic conditions, and while all of the intersections should be squared up with Highway 2A to minimize future operational problems, the design requirement (intersection type noted above) can be expected to change with time. Currently, both 63rd Avenue and Dickens Lane carry less than 2000 vehicles per day at their intersections with the service road and both are configured as Type I designs with approximately 24 metres of separation between the service road and Highway 2A. The existing configurations are therefore adequate, though they could require an upgrade to a Type II or III design with a median restricting movements to right turns only if accident frequencies were found to be problematic. These long term designs are discussed later in this report.
In the case of Heritage Way, a Type 2 design is required under existing conditions, which points to a possible need for signalization at Heritage Way/Highway 2A. However, the signal warrant analysis showed this intersection not meeting the warrants based on conflicting volumes, and further, signalization has been recommended at Woodland Drive/Wolf Creek Drive/Highway 2A immediately to the north. As such, signalization of both Woodland Drive and Heritage Way is not required in the short term as the signalization of Woodland Drive/Highway 2A is likely to draw traffic away from Heritage Way and onto Woodland Drive in order to access Highway 2A.
Since the Heritage Way intersection does not clearly fall into one of the categories described by TAC, it is recommended that the safety performance of this intersection be monitored. If the collision frequency rises to an unacceptable level, consideration should be given to installing a raised concrete median along Heritage Way that restricts the service road to right turns only. As well, a southbound to westbound right turn lane from Highway 2A should be constructed as an interim measure 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 Heritage Way that is waiting to turn left from westbound Heritage Way to southbound on the service road.
The westbound width of Heritage Way 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 metre 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.
In summary, then, both 63rd Avenue and Dicken’s Lane are currently adequate as Type I service road intersection designs with approximately 24 metre separation from Highway 2A. It is noted that these intersections will require upgrading to Type 2 or 3 designs by beyond the 20,000 population horizon. This is discussed in more detail later in this report. As well, it is recommended that the Heritage intersection be immediately upgraded to a Type II design as illustrated on Exhibit 4-4B.