Month: November 2019

New Changes for Designing Low-Volume Roads

While staying up-to-date on standards, manuals, guidelines, policies, and specifications can be challenging, the Hoyle, Tanner design teams have welcomed the Second Edition Guidelines for Geometric Design of Low-Volume Roads (Guidelines) recently published by the American Association of State Highway and Transportation Officials (AASHTO). The updated guidelines expand the definition of low-volume which provides greater flexibility to Hoyle, Tanner’s engineers to design the appropriate solution for the challenges our clients face. We’re going to cover some basics of the Guidelines and why it is so welcomed.

In the first edition (2001), low-volume roads were considered to have traffic volumes of 400 vehicles per day (vpd) or less. With the newest release (2019), the Guidelines expand coverage to roads with traffic volumes of 2,000 vpd or less. What does 400 vpd look like? For perspective: If you were to walk down a street, you’d expect to see one vehicle approximately every 3 ½ minutes at 400 vpd. If the same road experienced 2,000 vpd, you’d expect to see one vehicle approximately every 45 seconds.

According to the Guidelines, 80% of the roads in the U.S. are low-volume roads.

To determine if that 80% was applicable to our clients, we reviewed available traffic counts for an “average” New Hampshire town and found a conservative 70% of their road miles met the new definition of low-volume.

The Guidelines still remain focused on very low-volume roads (≤ 400 vpd) but the inclusion of roads with volumes of ≤ 2,000 vpd is greeted with open arms. This provides our design teams an additional resource on more projects; before the latest release we could not use the Guidelines on most of our projects as traffic volumes typically exceeded 400 vpd. However, a majority of past projects had traffic volumes that did not exceed 2,000 vpd.

What’s the benefit to our clients and designers


The Guidelines apply to both new construction and evaluating existing roadways. Here are a few things designers can consider for the construction of a new low-volume road:

Reduce pavement width allocated to vehicles, narrow the road. The obvious benefit to narrower roads is reduced construction cost. Another benefit is a decrease in environmental impacts. Thinking a little bit further beyond the edge of road, the savings from a narrower road could be invested in pedestrian and bicycle accommodations.

Reduce the design speed, allowing for the use of sharper horizontal curves. This could be used to avoid or minimize impacts to environmentally sensitive areas, an excessive cut, an excessive fill, or negative impacts to abutting properties. Doing any of these could not only reduce construction costs, but also potentially speed up the construction time and reduce the environmental permitting coordination.

Reduce the stopping sight distance, allowing for the use of sharper curves. Similar to reducing the design speed, however, this provides the designer flexibility for both the horizontal and vertical (profile) alignments. This could be used to avoid or minimize impacts to environmentally sensitive areas, an excessive cut, an excessive fill, or negative impacts to abutting properties. Doing any of these could not only reduce construction costs, but also potentially speed up the construction time and reduce the environmental permitting coordination.

Reduce the clear zone, and thus reduce or eliminate guardrail. A little side note, a clear zone is an area that allows a driver to stop safely, or regain control of a vehicle that has left the roadway. Since guardrail is a roadside hazard, costly to install, and costly to maintain when impacted, being able to reduce guardrail or eliminate it reduces construction maintenance costs and potential accidents involving it.

With this increased flexibility the Guidelines provide there is still engineering judgement to be used. For instance, it would be ill-advised to combine a narrow road with sharper curves and reduced stopping sight distance. Remember the intent of the Guideline is to reduce crash frequency and severity while prudently using public funds.


What about all the existing roads to be maintained?

We have the ability to evaluate how the existing road is performing and if it meets the Guidelines. When something doesn’t meet the Guidelines, that doesn’t mean that it needs to be fixed.

For example, let’s consider a one-mile segment of low-volume rural road in good condition, and we’re looking to resurface it before it becomes worse. We go out to the site, take measurements and notes of existing conditions, and find the following:

  • The average road width is less than the Guideline recommendation.
  • There is a curve that is sharper than the Guidelines minimum radius, has no warning signs, appears multiple vehicles have left the paved surface within the curve but no reported accidents in the last 5 years.
  • There are multiple trees within the clear zone but no signs of impacts or reported accidents.

There are several ways to address each of the issues. Recalling the purpose of the Guidelines is to make improvements at locations where it can be expected to provide substantial crash reduction benefits the design team makes a recommendation. Maintain the existing road width except within the sharp curve, where the pavement is to be widened to the Guideline minimum and the trees within the clear zone are to remain.

Hoyle, Tanner’s transportation design engineers are experts in roadway design, pavement layout, roadway stormwater, and safety for vehicles and pedestrians alike. We research and commit ourselves to learning the newest design guidelines for a safer, healthier community for drivers, roadway designers, and pedestrians. Questions? Call (603) 669-5555 ext. 181 or email me to discuss the latest technology and guidelines in the transportation engineering industry.

PFAS Contamination in New Hampshire Drinking Water: What Our Water Quality Experts are Learning about this Emerging Contaminant

picture of a faucet in someone's kitchen pouring water into a sink to show drinking water contaminants

The whatTeal circle with "NH PFAS Sources" written on top and inside circle, text explaining where PFAS contaminants originate in NH

Perfluoroalkyl compounds (PFAS) are manmade chemicals that are characterized by very stable carbon chains that allow them to act as a strong repellent to oil, water, and stains from other liquids. These desirable properties mean they are found in hundreds of consumer products as well as in firefighting foams.

There are more than 1,000 forms of PFAS compounds that have different chemical makeups and properties and different levels of toxicity. To date, the most commonly found PFAS compounds are ‘perfluorooctanoic acid’ (PFOA) and ‘perfluorooctanesulfonic acid’ (PFOS).

These forms have long carbon chains, do not readily break down in the environment, are water soluble, and have been found in some New Hampshire groundwater supplies at elevated levels.

The why

The public health concern is for PFAS to be consumed, absorbed and accumulated in the body at toxic levels. Although more research is needed, initial scientific studies indicate that long-chain compounds like PFOA and PFOS may cause developmental effects in infants, interfere with the body’s natural hormones, increase cholesterol levels, affect the immune system and increase the risk of cancer. Scientists are still learning about the health effects of PFAS and their toxicity, though it is believed that the PFAS compounds having shorter carbon chains are potentially less toxic since they remain in the bloodstream for shorter periods of time.

Are these compounds in your public water supply?

The who

In 2017, EPA recommended PFAS levels they believed would not lead to toxicity while allowing states to consider more stringent levels for compounds of concern. The NH Department of Environmental Services (DES) has been working diligently on amendments to their drinking water rules to protect public health and the environment from PFAS in our drinking water. New rules were recently adopted that will affect every public water system in the State of New Hampshire.

The when

Last week, Hoyle, Tanner’s water quality experts attended the NH Drinking Water Exposition and Tradeshow learning about New Hampshire’s new PFAS limits. DES submitted amended public drinking water rules in July 2019 to the state legislature which voted in favor of the new standards. The new standards became effective on September 29, 2019 setting  the Maximum Contaminant Levels (MCL) in public drinking water for specific PFAS compounds as follows:

  1. PFHxS = 18 ppt
  2. PFNA = 11 ppt
  3. PFOS = 15 ppt
  4. PFOA = 12 ppt

The new rules require public water supplies to begin sampling and reporting levels of these four PFAS compounds beginning in the fourth quarter of 2019 (Oct-Dec) with continued quarterly sampling and reporting in 2020 and beyond. The regulatory thresholds will be based on a 4-quarter running average for each of the PFAS compounds with compliance indicated by a 4-quarter average that is less than the MCL for each compound.

By January 2020, DES will be submitting draft rules on PFAS in surface water to the New Hampshire legislature – more to come on this front!

The how

Proper sampling is critical to avoid contaminating samples. Many communities are not equipped to perform the sampling themselves and will rely on certified laboratories for proper sampling, analytical methods, and meeting the quarterly sampling and reporting schedule.

The DES Water Quality Experts

Hoyle, Tanner’s water quality engineers are committed to keeping at the forefront of emerging regulations and technologies to be able to better serve the communities where we live and work.  You may contact me, Joe Ducharme, Regional Manager of Environmental Services, at 603-669-5555, x-142 or email me with any questions or water quality needs – we are here to help!

4 Things We Learned about Electronic Tolling in New Hampshire

all electronic tolling AET photo from MassDOT

A few weeks ago, we attended the New Hampshire Institute of Transportation Engineers (NHITE) fall meeting (where I serve as NHITE president). Our engineers learned about the history of tolling in New Hampshire, tolling technology, and details on design and challenges at planned All Electronic Tolling (AET) locations in Dover and Rochester.

Electronic tolls are just what they sound like – overhead scanners that connect to an account like E-ZPass to pay your toll. They replace the manned/unmanned booths (barrier tolls) and the need for rolls of quarters or tokens. They help with alleviating traffic that builds up at toll booths during peak seasons. Just like barrier toll booths, though, they have their challenges. Fee collection systems must be properly designed and monitored to ensure revenue is not lost while driver privacy must be protected.

These are all considerations that engineers and system administrators must consider when thinking about implementing AET.

Key takeaways we want to share

  • Collecting tolls is vital for maintaining turnpike assets in New Hampshire; including nearly 90 miles of limited access highway such as the FE Everett Turnpike.
  • AET tolling increases the capacity of the toll facilities and reduces the congestion felt by drivers. They eliminate vehicle conflict points at merge locations and lane changes, which helps to reduce crashes. AET also reduces environmental impacts with a smaller project footprint and by lowering emissions through reduced acceleration/deceleration.
  • Drivers’ privacy is a primary concern; data that is collected by electronic tolls is erased immediately after all successful transactions.
  • Loss of revenue through “leakage” (travelers who go through the tolls without paying) must be minimized so that funds for road maintenance and repairs are available.

How this will help you

Attending conferences and trainings like these helps Hoyle, Tanner staff keep abreast of the latest technologies and ideas that we can use to better serve our clients.