Street Snow Plowing FAQ 

Frequently-Asked Questions about Street Snow Plowing 

  return to www.a2gov.org/snow

Questions and Answers:

1.  Are vehicles allowed to pass a snowplow?
There are no state laws that prohibit passing a snowplow. However, the action of passing can be extremely dangerous because pavement conditions vary across the path taken to pass. The majority of crashes involving snowplows and vehicles happen when a snowplow is rear ended or hit while being passed.

2.  What should be kept in mind when shoveling/plowing driveways?
Property owners and snow removal contractors should be aware that shoveling or plowing snow from driveways onto or across roads is illegal (Act 82 of 1978, vehicle code 257.677A) because it can present a serious traffic hazard to motorists. Instead, pile the snow behind the curb or shoulder on your side of the road. See the question #3 below for more details on maintaining driveway openings.

3.  How can I avoid having a city plow truck push snow into my driveway after I clean it?
Throughout the winter months, city crews will be out clearing the roads during and after snowfalls. At the same time residents are clearing their driveways. Many times while this is going on, a snowplow truck will go by and fill in the end of a freshly cleared driveway with snow from the road, causing frustration and more clearing for residents. Please understand that the city’s first priority is the safety of the traveling public and clearing the roads of snow and ice and pushing it off of the road and shoulders, and sometimes into driveways, is a necessary wintertime evil.

So why does the city push the snow off the road onto the shoulder, only to come back and push the snow farther back on the shoulder? The truck usually makes one pass to open the road up so residents may get in and out. Then the truck come back to widen the road, and then the shoulders for future snow accumulation. Residents sometimes call and ask why we cannot pick up the blade when going by their driveway. This is not a practical solution and our drivers would never finish clearing the roads due to the multitude of driveways. There is, however, a method of clearing your driveway that can help minimize the amount of snow (and frustration) during the winter months:

• If possible (not always practical), clear your driveway after we have finished plowing the roads.
• When clearing your driveway, place as much snow as possible in the direction of travel, on the downstream side of the road.
• Clear an area upstream from your driveway opening to form a “pocket” for the snow from the road to go into. The result? More of the snow from the road will go into the pocket and less will land in the end of your driveway. (Please see the diagram below.)

4. Why does a street plow leave snow on sidewalks, especially at the bottom of crosswalks?
The city is aware of the difficulty snow plowing can create for sidewalk clearance, particularly at corners. The city works with plow drivers to reduce this situation the best we can. However, given the crowded nature of streets and the volume of snow we are dealing with, snow at sidewalk intersections can pile up similar to the situation facing the bottom of driveways. Property owners may need to use ice melt and metal shovels if the snow has become very packed down.

Property owners are always responsible for clearing snow and ice along their sidewalk frontage in accordance with city Ordinance, and someone can be fined if a snow plow pushes snow onto the sidewalk, even after shoveling.

5. A City plow truck knocked over my solid waste container.
Please call us at (734) 794-6362 and city staff will clean it up at their earliest convenience. Occasionally this happens even when the container is placed on the grass extension due to the force of the plowed material striking the container and the plow driver is not aware it occurred. On residential streets plowing is scheduled to avoid the solid waste pickup day section until collection is completed, but on major roads that receive ongoing winter maintenance all the time it is not possible to avoid conflicts.

6. The plow was speeding past my house.
Our drivers are required to follow all applicable laws and will be held responsible for violations. Please provide the time and location and if possible the vehicle number for us to follow up. Please be aware that frequently the trucks are in a low gear and using high engine RPM to maintain the power necessary to push the snow; this creates the impression that they are speeding. Additionally the truck size, engine and plow blade noise, and flying debris make judgment of speed by an observer difficult.

7.  A city plow knocked over my mailbox.
Please call the city at (734) 794-6362 if this occurs. Staff will install a replacement mailbox at their earliest convenience. The replacement mailbox will consist of a standard 4x4 treated post and standard US Postal service approved box. A temporary replacement maybe installed due to time constraints or site conditions. All replacements shall comply with national traffic safety standards and postal service requirements. 

8. The Post Office says they can’t access my mailbox and won’t deliver my mail.
Maintenance of access for postal delivery is the mail customers’ responsibility. Several reasons may prevent the plow drivers from getting closer to your mailbox, including: blocked access due to ice,  snow,  or landscaping that endangers the driver or risks damage to the mail vehicle if they approach closer; and improperly-installed mailboxes that encroach on the drivable road surface. Sometime attempts to push the snow over further results in damaged mailboxes due to the force of the snow against the post.

9. A city plow buried my landscaping, yard decoration, or basketball net with snow.
Occasionally, items placed in the public right-of-way may be damaged by snow removal operations. Please remove items such as portable basketball hoops, lawn ornaments, statuary, etc., so they do not become damaged. The city is not responsible for damage to items left in a street's right-of-way.

10. The fire hydrant is blocked with snow.
Adopt a fire hydrant! Do a good deed for your community - clear snow away from fire hydrants. This provides quick access for firefighters and water maintenance workers in case of an emergency.

11. My residential street is still covered with snow even after it was plowed. Why doesn’t Ann Arbor use more salt on roads?
Many years ago the Ann Arbor City Council passed a resolution to switch from applying 100 percent salt (sodium chloride) to using a mixture of 95 percent sand and 5 percent salt onto public streets. This decision was based on research and recommendations from the Huron River Watershed Council, which found significant salt contamination in the Huron River. High levels of salt in the Huron River result in poisoned fish and aquatic plants and increased costs to process the river water into drinking water at the municipal Water Treatment Plant. Road salt can also have a detrimental effect in neighborhoods by stunting grass and trees and by promoting rust on the metal undersides of vehicles. Consequently, it is a city policy to apply the least amount of salt that allows for safe driving. The amount of salt used depends on snowfall rates, time of day, and pavement conditions. Salt is not effective when pavement temperatures are below 18 degrees F. The city uses portable readers to determine pavement temperatures. Under icy conditions, sand may be applied to provide road friction until the salt can begin to work. Because sand clogs street gutters, using sand requires additional maintenance to sweep streets and clean drains.

12. Why doesn't the department use more sand?
Our experiences, and the body of research on the use of sand, indicate the benefits of abrasives (sand) applied to roadways are very minimal. Abrasives are easily displaced from the roadway by traffic and have no ice melting properties. There are also negative environmental consequences such as siltation of waterways.

13.  What are the limitations of road salt?
The minimum practical application range for salt is a pavement temperature of 15-20°F and above. While salt will melt snow and ice down to a pavement temperature of -6°F, it can melt over five times as much ice at 30°F as at 20°F. Thus the effectiveness of salt is sensitive to small differences in pavement temperature. The city will attempt to apply only the amount required for temperature, time and use. Too little and the roadway will refreeze, too much is a waste of money and resources.

When the pavement temperature drops below 15°F the effectiveness of salt is decreased significantly. At these lower temperatures, the city will typically cease straight salt applications and begin adding chemicals to the salt such as calcium chloride or magnesium chloride that will lower the freezing point even further.

Wind conditions must also be considered when deciding on whether to apply salt or other de-icing agents. As the temperatures drop and the snow becomes dryer, the wind can begin to blow the snow across the pavement. If there is a chemical residue left on the pavement from a previous salt application, blowing snow can be attracted to the residue and stick to the pavement creating hazardous conditions that would not have existed if no de-icing agents were previously applied. This is why we are sometimes reluctant to apply salt or chemicals when the pavement temperatures are below 15°F. The effectiveness of salt can also be affected by the type of pavement. For example, salt works better on new asphaltic (blacktop) pavements than on tined concrete pavements. The salt being used today typically includes other ice melting de-icing agents to increase its effectiveness at lower temperatures and to help it better adhere to the pavement. Adding other de-icing agents to the salt also reduces the number of applications needed. The City of Ann Arbor is always looking for new ways to reduce the amount of chlorides needed to return the roadways to safe winter driving conditions. Sometimes counties use sand and other abrasives at lower temperatures to improve friction on the roadway. Abrasives have no ice melting properties and thus their use is limited.

The graph above shows that salt melts more ice per pound at higher temperatures. The graph at right shows the comparative time for different compounds to melt 1/8" of glare ice. "Wisconsin Transportation Bulletin No. 6: Using Salt and Sand for Winter Road Maintenance" (revised March 1996 © 1996, Wisconsin Transportation Center).

14. Why apply salt to the roadways in the winter?
Salt is used to make the roadways safer during the winter. Salt lowers the freezing point of snow and ice and keeps the snow "workable" so it is more easily removed. Salt can be used for anti-icing, de-icing, or melting. Anti-icing is a technique where a chloride is applied to the roadway prior to a storm to prevent the snow/ice from bonding to the pavement. De-icing and melting is when a chloride is applied after the storm has begun in order to break up ice and snow pack or to melt glare/black ice.

15. Why would salt be spread on a bare highway after a snowstorm is over?
The projected temperature of the road surface will influence the treatment of a road. If plowing operations have finished and a road is left in “black and wet” condition, there is sometimes a danger of the water re-freezing on the road. There are times, especially at night, when a post-storm salt application may be necessary.

16. What is the importance of pavement and subsurface temperatures? Why can't you just use air temperatures?
The ability of de-icing agent to melt snow and ice depends on the temperature of the roadway and not the air temperature. During autumn the pavement is often kept warmer than the surrounding air because of the warm soil. During spring the reverse may be true. The pavement temperatures can be colder than the air because the soil is still frozen from the low winter temperatures. The sun also has a strong influence on the pavement temperatures. It can help heat the pavement and speed the melting process. Air and pavement temperatures can often differ by as much as 20 degrees Fahrenheit. For example, on a recent bitterly cold early winter day the air temperature was below 4°F and the pavement or surface temperature was 24°F, primarily because the subsurface temperature had not yet dropped as far below freezing.

17. Why is there a difference in street maintenance performance from storm to storm?
One of the biggest factors that determine the city’s performance is the type of storm and range of temperatures. There are reportedly more than 60,000 combinations of winter storms that can hit Michigan during the winter and each storm poses unique problems to snowplow operators. Storms with low temperatures can be difficult because de-icing agents become less effective at the lower temperatures. Storms with high winds also are a challenge because the snow quickly blows back onto the roadway after the plows pass. 

 
18. Why are you spraying water on the roadway on a perfectly clear day?
We are actually spraying a liquid salt solution on the roadway that will help keep snow and ice from bonding to the pavement. Spraying a salt solution on the roadway is similar to spraying a frying pan with oil to keep food from sticking to the bottom of the pan. The salt solution acts as a barrier so that the snow and ice won't form a strong bond to the pavement. Studies show that under extremely cold conditions ice frozen to concrete has a stronger bond than concrete alone. In many locations we also spray the salt solution on bridge decks the afternoon before a predicted frost. The early application of the salt solution helps prevent frost from forming on bridge decks throughout the night.

19. Why is it that I never seem to see a snowplow during a winter storm?
The city’s street maintenance unit is responsible for snow removal on 358 lane miles of salt route roadway and 10 bridges. Using 10 trucks on a normal shift the average time to complete a salt route is approximately 1½-2 hours, but some cycle times can be as long as four hours. Time is also needed to load and reload the truck with de-icing materials. The number of lane miles, if placed end to end would take you from Ann Arbor to Newberry, MI.

Winter maintenance operations will be conducted based on a priority system established on the city and state Trunkline roads. The priorities primarily have been established based on traffic volumes.

Priority 1 - State Trunklines
Priority 2 - High volume hard surface roads
Priority 3 - Medium volume hard surface roads
Priority 4 - Subdivision streets
Priority 5 - Gravel roads, alleys, dead ends and Cul-De-Sacs

21. We pay property tax, why don’t we get better snow removal service?
The property tax you pay is used for your local and county governmental units and for schools, not for day-to-day road maintenance. The city’s street maintenance budget is funded solely by the gas tax and vehicle registration fees passed on by the State of Michigan in compliance with Public Act 51. This income funds all day to day maintenance activities including traffic signals, signage, pavement markings, sweeping and both temporary and permanent pavement repairs. The portion of your property tax bill as part of the voter-supported Street Millage may only be used for street and bridge resurfacing and reconstruction purposes.

22. Why is the city promoting bicycle commuting and then not clearing the bike lanes better?
Total snow and ice control in the on road bike lanes is a difficult task due to the nature of location and level of use. Bicycles lack the tire size and weight to effectively crush and move the salt granules around to promote melting action. Additionally, the lack of heat from tire friction and drivetrain radiation limits the effectiveness of salt applications. The location of bike lanes at the edge of the road also subjects them to run off from melted snow plowed to the edges. This daily runoff refreezes.

 return to www.a2gov.org/snow