Traffic Engineering - Traffic Impact - Assessment Answer

Traffic Engineering

Case Scenario/ Task

Conduct a Traffic Impact Assessment for a proposed development as shown in the following figures, located on North Creek Road with frontage to Henderson Lane and Hutley Drive, Lennox Head. The development comprises of 149 lots plus an integrated housing facility which has 30 lots, resulting in total of 179 residential lots.

The site is currently predominantly cleared land. It is proposed to realign North Creek Road through the subject site, with Hutley Drive extended to intersect with North Creek Road via a four leg roundabout. Henderson Lane will also be realigned to intersect with North Creek Road via a new T junction, to the west of Stoneyhurst Drive. The proposed site layout, shown below, is also provided

It is assumed that the development will be completed in 2020. A future planning horizon of 10 years from the date of completion should be considered. The impact of the development at the development completion year and at the planning horizon should be assessed.

For each scenario, analyse the operation of the two intersections, Hutley Drive/New North Creek Rd and The Coast Rd/Ballina St/New North Creek Rd, in the AM and PM peak hour. Note that the Hutley Drive/New North Creek Rd is only required to be analysed for the scenarios with the development, as this roundabout will only be constructed as part of the

development. If the operation of any existing or proposed intersection is unacceptable, recommendations to achieve acceptable operation (which have been tested in SIDRA) should be included. Thus the report should include details of the form and lane configurations of the intersections at Hutley Drive/New North Creek Rd and The Coast Rd/Ballina St/New North

Creek Rd intersections that should be constructed.

The following assumptions apply to the proposed development traffic:

• A directional distribution of development traffic to/from north or south of 50% and 50% respectively. The directional distributions described apply to AM and PM peak volumes, both entering and exiting the development.

• For the development traffic to/from the north, 60% are assumed to use The Coast Rd (i.e. left turn on The Coast Rd for exiting traffic), and 40% assumed to use Ballina Rd (i.e. through movement onto Ballina Rd for exiting traffic).

• For the development traffic to/from the south, 25% are assumed exit the

development to the south (i.e. not use the to use The Coast Rd/Ballina St/New North Creek Rd intersection) and utilise Skennars Head Rd, while the remaining 75% are assumed to use The Coast Rd/Ballina St/New North Creek Rd intersection (i.e. left turn onto The Coast Rd for exiting traffic).

• Assume a split for the trip ends for the development of 20% in and 80% out in the AM peak and a 70% in and 30% out in the PM peak.

The following assumptions apply to the background traffic:

• An annual growth of 2% for the existing (background) traffic.

• When distributing the background (existing) volumes at the new Hutley Drive/New North Creek Rd intersection, assume 1/3 from the east (i.e. via the new Hutley Rd connection) and 2/3 from the south (i.e. via the New North Creek Rd). The following are provided on MySCU Blackboard to enable the assessment:

• RTA Guide to Traffic Generating Developments

• AM and PM peak hour turning movements counts for the current The Coast

Road/North Creek Road/Ballina Street intersection conducted in March 2013

• The proposed site plan for the development

• The marking criteria

The outcome of the traffic assessment is to be submitted via MySCU Blackboard is a Traffic

Impact Assessment. The report must be more than 10 pages in length (excluding appendices) with an appropriate report structure, including SIDRA results, title pages, tables of contents, references, conclusions and recommendations etc. All assumptions should be well documented in the report, and the traffic volumes for each scenario must be included.

Appropriate inclusions and structures of Traffic Impact Assessments were discussed in lectures, with a sample Traffic Impact Assessment provided for information. Use this as a guide only not as a definitive template.

The main aim of this report is to assess the traffic impact of the proposal to develop 149 lots along with an integrated housing facility consisting of 30 lots. This site of construction of 179 residential lots is located on North Creek Road with frontage to Henderson Lane and Hutley Drive. The potential impact of the development on the surrounding and internal road network will be addressed in this report.

1. PROPOSED DEVELOPMENT

   • Subject Site

The subject site is located on North Creek Road and has frontage to Henderson Lane and Hutley Drive as illustrated in figure 1.

• Proposed Plan of Development

The proposal is for a residential land of 149 lots with an integrated 30 housing lots. Currently the site is a clear land. Proposal has been made to realign North Creek Road through the subject site; Hutley Drive will be extended to intersect with North Creek Road via a four leg roundabout. Henderson Lane will also be realigned to intersect with North Creek Road via a new T junction, to the west of Stoneyhurst Drive. The proposed site layout is as shown in figure 2.

1. EXISTING ROAD NETWORK

   • Existing Roadway Network

The Coast Road is a part of north-south major route between Byron Bay and Ballina and has two traffic lanes. The posted speed limit near North Creek Road is 60km/hr. North Creek Road is also a two lane road with a speed limit of 60km/hr. Hutley Drive currently connects the concerned site and Henderson Lane and has a speed limit of 50km/hr. Henderson Lane is a two lane road with a pavement width of approximately 7 m and a speed limit of 50 km/hr. The intersection of the Coast Road, North Creek Road and Ballina Street is regulated by a two lane circulating roundabout. Figures 3 shows the road network and its surrounding interactions.

In March 2013 traffic counts were conducted at the Coast Road, North Creek Road and Ballina Street. Figure 4 summaries these results.

• Estimation of Future Traffic Conditions

Here a growth rate of 2% p.a. was applied to existing traffic volumes at the Coast Road, North Creek Road and Ballina Street intersection. This represents a typical traffic growth rate for a regional area. Figure 5 shows the resultant estimates of traffic volumes in the year 2024.

1. DEVELOPMENT TRAFFIC ESTIMATES

   • Estimated Development Traffic Volumes

The following traffic generation and distribution characteristics have been adopted:

Table 1: Adopted Traffic Demand and Distribution Values

The proposed development comprises 149 detached lots and an integrated housing of 30 lots.

Application of the above values to the proposed development yields a peak hour traffic generation potential of 161 vehicle trips as follows:

Table 2: Estimated Traffic Generation Potential

As per Cardno Eppell Olsen assessment, it is assumed that the majority (75%) of southbound traffic will utilize The Coast Road / North Coast Road / Ballina Street roundabout and only a limited percentage (25%) will use Skennars Head Road via north Coast Road.

Figure 6 shows the estimates of development traffic volumes at The Coast Road / North Coast Road / Ballina Street roundabout.

1. TRAFFIC IMPACT ASSESSMENT

   • Scope of Assessment

The traffic inferences of development proposals primarily concern the effects that any additional traffic flows may have on the operational performance of the nearby road network. SIDRA program can assess these effects. For this assessment, a capacity analysis has been done using the data during the critical afternoon peak period of The Coast Road / North Creek Road and Ballina Street intersection.

• Intersection Capacity Analysis

The intersection has been modeled under current and projected future (year 2024) traffic conditions, without and with the proposed development. The intersection geometry is shown in Figure 7. Detailed results of the SIDRA analysis is provided in Appendix I and summarized below.

Table 3: SIDRA Results – The Coast Road / North Creek Road & Ballina Street Intersection

The results indicate that the intersection can operate satisfactorily over the next 10 years with the proposed development traffic. The degree of saturation will remain below 0.8. Total average vehicle delays at the intersection will be less than 14 seconds and 95^th percentile queue lengths will be no greater than 9-10 vehicles. The existing roundabout is therefore fine for the proposed development traffic.