Already this winter many locations in Idaho have received historic amounts of precipitation, much of it as snowfall. Along with this precipitation have been weeks of unseasonable cold with several days of rainfall in between. What does this winter’s harsh conditions mean for the spring? We should prepare to deal with unprecedented levels of pavement breakup.
As your organization undoubtedly continues to struggle through the season with these challenges, consideration must be given now as to how best to protect your system during the coming spring thaw.
What’s going on?
Due to record snowfalls and higher levels of water in and beneath the asphalt pavement, you are likely to experience a spring breakup period worse than ever before. As winter moves toward spring, warmer temperatures make the subgrade less stiff and because of less bearing capacity the road surface tends to break up and generally deteriorate. This period of time has the potential to cause the greatest weather related damage to your system. Many may not be familiar with how to identify early signs of trouble or the tools available to help reduce this damage.
What should we do?
Heavy loads pose the most damage potential to roadways during spring breakup. Therefore, there are provisions in Idaho State Statute and related rules that allow you to limit or restrict the weight and speed of commercial vehicles over 10,000 pounds on your road system. While there has been significant work to scientifically deal with determining when and how long to implement restrictions on roadways, the Local Highway Technical Assistance Council (LHTAC) offers the following strategy for identifying and implementing restrictions on local roads within your jurisdiction:
1. Preparation – These areas may give you an early indication of trouble
- Determine all sections of road that have had breakup problems in past years.
- Determine road sections that have transverse cracking, longitudinal cracking or alligator cracking.
- Identify areas where water has pooled over the roadways during thaw periods.
- Do you have weight and speed restriction signs? Find out where you can get them.
2. Monitor all roadways – Immediate concerns
- Pot holes.
- Water seeping from cracks.
- Raveling of the pavement edge.
- Noticeable pavement deflection.
3. Implement weight and speed restrictions – based on failure indicators listed above
a. Post a sign at the beginning and end of the restricted segment of roadway for one of three maximum weights (see attached sign details).
- 16,000 pounds on any axle.
- 14,000 pounds on any axle.
- 12,000 pounds on any axle.
b. When posted for weight limitation, speed is limited to 30 MPH. Restricted speed zones will be posted on an existing sign post as follows
- A 6 X 18 red marker will designate the beginning of the speed restriction.
- A 6 X 18 yellow marker will designate the end of the speed restriction.
LHTAC is here to help!
Additional information is provided on the attached sheet if you would like to review this subject in greater depth. As always, LHTAC is ready to assist you by answering any questions or by helping your agency find available resources.
If you have questions or need assistance please contact Lan Smith at LHTAC, 208-344-0565.
Reference Information
http://apps.itd.idaho.gov/apps/manuals/Traffic_Manual.pdf
The following is an excerpt of the Idaho Transportation Department Traffic Manual:
Idaho Statute 49-1005 – Special Regulations and Notice – gives ITD authority to reduce the permissible size, weight, or speeds of vehicles operating on a highway for a period of time for the protection of the highway or for public safety due to climatic or other reasons. IDAPA 39.03.14 – Rules Governing Policy During Spring Breakup Season – provides additional information about the application of the statute.
Use Weight Limit signs (R12 Series) when vehicle weight loadings are restricted to a maximum weight or maximum weight per axle. Use the BEGIN (R3-9cP) and END (R3-9dP) plaques to inform road users where the weight limit begins and ends. Use additional Weight Limit signs (R12 Series) within the restricted section of highway at intersections where overweight vehicles may enter the highway.
Because climatic conditions that cause weight restrictions are usually regional, detours for vehicles weighing more than the posted limit should generally not be provided.
IDAPA 39.03.14 – Rules Governing Policy During Spring Breakup Season – provides information about marking highways when speeds for trucks and busses with a gross weight of 10,000 pounds or more are restrictions due to climatic or other conditions. Use red, yellow, or green markers to indicate the status of the speed restriction. A red marker indicates that the speed is restricted to 30 mph. A yellow marker indicates that the posted speed may be resumed. Green markers may be used when the District Engineer temporarily waives the spring breakup restrictions.
When used, attach 6 x 18 inch red, yellow, or green markers vertically to existing sign posts along the highway segment where speeds are restricted. The markers should usually be attached below Speed Limit (R2-1) signs, but can be posted below other highway sign. Do not cover or alter existing Speed Limit (R2-1) signs. End the restricted speed zone with one or more yellow markers.