ENTR613 Highway Geometric Design Assessment 2025 | UC

ENTR613 Introduction

The major part of this course will be an individual design project to prepare a realignment design for a section of sub-standard two-lane rural highway. Students will use the theory and practice presented in the course to develop a suitable horizontal/vertical alignment and cross-sections.

This will be based on Austroads Guide to Road Design (GTRD) highway design standards. In general, students should base their design on the GTRD, but are welcome to refer to other standards/guidelines where necessary.

Hand drawings and calculations, as detailed below, will be worked on between the first and second teaching blocks. At the end of the first block, students will have a computer lab session and use the Department’s 12d software to create their design electronically and to generate the necessary plans and sections. A final report will then be prepared showing plans/sections and documenting design calculations and assumptions.

Students will also be expected to provide fortnightly reports on the progress of their design project and associated background reading in between the block courses. The course coordinator will send out regular emails to announce this, and students will be expected to respond to these within 1 week (a small proportion of marks is allocated for regular responses). Students are also encouraged to use the Learn Discussion tool to raise any course-related issues/questions with their classmates and lecturers – ALL are expected to contribute to these discussions.

Information to be Supplied to the Student

Accompanying these project details is the following information:

• Two A3 contour maps of the existing road alignment (Taylor Road) and surrounding terrain (separate hard copies and also available on Learn as PDF).
• Longitudinal section of the existing road environment (Taylor Road) – four sheets (separate hard copies and also available on Learn as PDF).
• A crash listing from CAS of recently reported injury crashes in the vicinity (end of this document).
• The AADT of the road section (Taylor Road) is 3900 vehicles/day with 10% HCVs. The AADT of the side road (Hills Road) is 450 vehicles/day.
• The existing road is generally 7.0 m wide, with 3.5 m lanes and no shoulders.
• Observed mean travel times on the existing road from Chainage 0 to Chainage 1900 are: o Northbound: Car = 95 s, Truck = 107 s o Southbound: Car = 92 s, Truck = 104 s
• It can be assumed that, below the (Grade 2) chipseal surface, the new road will require 150mm of M/4 basecourse on top of 200mm of AP40 sub-base material.
• The soil in this area can slope (in cut or fill) as steep as 1H:2V (not 1V:2H) without requiring structural support (e.g., retaining walls). Cut/fill higher than 8m will require benching.
• Adjacent road sections on either side have speed environments (in both directions) of 90km/h (south end) and 95 km/h (north end) respectively.

Minimum Requirements for the New Design

Each student will need to design a new alignment to replace the existing highway, subject to the following constraints:

• The new alignment must provide a high-speed environment that is substantially better than the existing (better fitting with adjacent road sections) and also enable drivers to achieve a reasonably consistent speed over its length.
• The new alignment must start before Chainage 080 on the existing road and finish at Chainage 1900.
• The new alignment must have at least one left-hand and one right-hand horizontal curve, with curve radii <1000 m.
• The new alignment must have at least one crest and one sag vertical curve.
• Sag vertical curves are designed for unlit conditions at night and comfort level with (vertical acceleration =0.05 g)
• The edge of formation of the new alignment should ideally avoid the existing buildings by at least 20 m (otherwise, provide some documentation justifying your alignment decision).
• The edge of formation of the new alignment should ideally avoid and/or relocate existing lakes/ponds by at least 10 m (otherwise provide some documentation justifying your alignment decision).
• The new alignment must provide earth-fill box culvert crossings over any streams.
• The existing uncontrolled T-Intersection of Taylor Road with Hill Road must be replaced with an intersection that connects Hill Road with the new alignment and provides some form of control.
• Studies of the geological stability of the eastern bank of the Big River have determined that an area of weak soil lies between Chainage 1200 and Chainage 1440. The edge of formation of the new alignment must therefore not be less than 20m from the river edge (on this side) in this zone.
• The new alignment should be fitted with clear zones as per Part 6 of GTRD. If your design deviates from the GTRD standard, you must provide appropriate reasoning (a design exception) for why your design does not comply with the GTRD standard.
• Assume Taylor Road is to remain in use while the new alignment is constructed.
• The total volume of earthworks cut should roughly balance the amount of fill required (within 20% or 10,000 m3).

Design Decisions and Calculations to be determined before the Second Block

Students will need to undertake the following tasks ahead of the second block course (these need to be appropriately documented):

Speed Environment and Design Speeds

• Examine the existing road alignment and assess the existing speed environment & operating speeds.
• Locate the ends of the new alignment and determine some horizontal curve intersection points (note the coordinates of these – you will need them for entering in 12D or Road Eng).
• Iteratively determine suitable horizontal curve radii, curve design speeds, and the overall speed environment for your new proposed alignment.

Horizontal Alignment Design

• Determine suitable maximum super-elevations for each curve and calculate the required transition curve lengths.
• Estimate the super-elevations along the road at 20 m intervals.
• Calculate the minimum offset required to clear obstructions on the inside of each curve to enable sufficient stopping sight distance to an object to be achieved.
• Set out and plot by hand the indicative centreline location of the chosen horizontal alignment on the contour map. Annotate key parameters of each design element (e.g., length, radius, PIs)

Vertical Alignment Design

• This part will be covered in detail in the second block; however, students are recommended to make a start reading between the two blocks.
• Plot by hand a long section of the natural surface along the proposed centreline (this will differ from the existing road long-section).
• On the plot, determine suitable locations for vertical curve intersection points (again, note these for 12D or Road Eng software).
• Calculate gradients of all vertical grade lines.
• Calculate suitable K-values for all sag and crest curves to enable adequate stopping sight distance to an object.
• Set out and plot by hand the indicative centreline location of the chosen vertical alignment on the long section. Annotate key parameters of each design element (e.g., length, K-value, PIs). Note: You should aim to balance cuts and fills reasonably well.

Cross-Section Design

• Design and draw a representative “typical cross-section” in both cut and fill situations (one each side). Include the pavement layers down to the formation level (below the sub-base).
• Identify a suitable location and type for an overtaking opportunity on your new alignment and determine the required length (including any tapers).
• From the terrain plan, estimate and draw the expected cross-section profile of your new alignment at two locations chosen from the given Sections 2 to 6 (show also the natural surface profile). Calculate the amount of cut and fill required for each section to construct to the formation level.

Miscellaneous Design Tasks

• Identify other likely design features such as drainage/culverts, and adjustment of other natural or manmade features.
• Draw an indicative sketch (to scale) of the proposed overtaking facility, showing all markings and dimensions. If dimensions (e.g., shoulder width) or pavement markings (e.g., centreline) differ from NZTA standards, explain why.
• Identify a suitable location for the intersection of Taylor Road and Hill Road. Draw an indicative sketch (to scale) of the proposed intersection, showing all markings and dimensions.

Note: For design checking during the second block, the above information does not have to be presented in typed or CAD form; neat hand notes and drawings will be perfectly adequate (graph paper may come in handy). The key is to ensure that they are understandable and readable by another person. All references to values/statements from GTRD or any other design sources must be clearly identified for checking later by others.    

Information to be Provided in the Final Report

As well as the calculations in typed format and design work undertaken above, students will also need to present the following information in their final reports:

• Include the design checklist completed during the second block.
•  Generate a horizontal plan and long-section of your final alignment (both A3) using 12d or Road Eng or any other available software package. Make sure it is suitably annotated (by hand or CAD) with the key parameters of each road design element.
• Generate and plot cross-sections at 20 m intervals along the new alignment, showing both the design profile and the existing natural surface. Annotate if necessary, particularly where you have modified the typical cross-section profile to allow for site-specific treatments (e.g., retaining walls, barrier fences). Determine the total quantities (m3) of cut and fill required by the alignment.
• Calculate the estimated quantities of pavement materials (m3) and road surfacing (m2) required for this project.
• Estimate the free-speed (unimpeded) travel times on the new alignment in each direction for a typical passenger car and semi-trailer truck.
• All material presented should be suitably ordered, with appropriate reference to included plots or Appendices where necessary. No more than a brief covering overview is necessary.
• An electronic copy of the design files used in your project, sufficient so that your design can be reproduced, should be zipped and submitted using the electronic dropbox to be provided on Learn.

Note: All material presented in the final report should be either in typed or CAD form or very neat handwritten notes and drawings. 

The Final Report (worth 30%) will be due about one week before the final exam (date to be confirmed), i.e., approximately the first week of October.

ENTR613 Existing Crash Data for Design Project