Driving the freeways around Ann Arbor, Michigan, is frequently adventurous. This GIS project will involve performing a detailed case study of the Ann Arbor freeway system in a geographic setting. The Ann Arbor freeway system consists of three freeways-- I-94, built in the late 1950s and early 1960s, M-14, completed in 1965, and US-23, completed in the early 1960s.  These routes are fully limited-access freeways with two lanes in each direction, with the exception of the 3 mile, 3 lane US-23/M-14 segment.  This project will pinpoint research questions by examining various aspects of the natural and human environments surrounding the freeways. As an outsider, I bring an interesting perspective to the process of analyzing the freeway system. I enjoy driving and I am familiar with cities whose traffic patterns are laid out as grids. I am also used to driving on rural interstates or on urban interstates that have multiple lanes of traffic.  In Ann Arbor, I see differences which I do not understand. The purpose of this project is to explore these differences and understand why they exist. Because an agreement between the City of Ann Arbor and Ann Arbor Township allows annexation of all township land within the US-23/I-94/M-14 limits in 2007, this research might have practical applications for the future.  Speed limits on the freeways could be affected, and the annexation of additional land could require additional sewage lines and other features to conform to city code.  The City of Ann Arbor, most importantly, will be freer to make decisions about the freeway network, without having to negotiate compliance from some other entities, although the Michigan Department of Transportation (MDOT) will still share a key role.  This could allow the City of Ann Arbor to continue planning for future development and sprawl on an even greater scale.  While a study of the entire street network would be fascinating, the researcher has chosen to limit the study to the freeway system.  In what might be termed a transformation, the researcher has essentially created several layers, units of analyses, or distinct categorical entities, out of one GIS layer: the street network.  The researcher has created a hierarchy with the freeway network at the top, followed by through routes with interchanges at the freeways, and at the bottom of the hierarchy are local roads with no freeway contact.  The GIS is just a portion of this study; more technical, conceptual, and side research all contribute to round out this project.  Nonetheless, the GIS has been a useful tool in being able to zoom in on specific sites to collect data more precisely.  The only limitation is that zooming in using a GIS can create additional error that must be noted.



This map, available from MDOT, gives a precise but not necessarily accurate traffic count of the number of vehicles traveling the Ann Arbor street network on a typical weekday.  It has two limitations; first it cannot account for traffic that is heavier in one direction than another, and secondly, it fails to tell us exactly when the traffic is heaviest and what the traffic counts are at those times.  Still, it will serve as a baseline for making projections.


Before we can answer the questions, "should anything be done?" and "Can anything be done?", we must first understand how the system developed and how this affects the modernization process.

THIS DATA IS COURTESY OF http://members.aol.com/hwys/MichHwys/MichHwys.html




Western Terminus: I-94 at EXIT 171 west of Ann Arbor.
Eastern Terminus: Junction of I-96 & I-275 on the City of Livonia/Plymouth Twp boundary.
Speculation exists that the entire route of M-14, once modifications are completed, will be re-designated I-394 and become part of the Interstate Highway System. Currently, plans are underway to improve the M-14 freeway in the area of Main St, the Huron River, and the Whitmore Lake/Barton Dr exit on the north side of Ann Arbor.  Much of the work has been completed. Currently, the portion of M-14 in the area of the Huron River is substandard freeway from federal specifications, with no shoulders, short acceleration and deceleration lanes, and even a stop sign on the Barton Dr on-ramp.  Once those modifications have been made, one source at MDOT claims that MDOT will push for an I-394 designation from I-94 to the I-96 & I-275 junction in Metro Detroit, making the freeway part of the federal interstate system.

History of the M-14 Freeway:

1964 - A new freeway connecting M-14 with US-23 northeast of Ann Arbor and the junction of M-14 & M-153 opens. The M-14 designation is run west along this new freeway, then west along US-23 across the north side of Ann Arbor, then south along BUS US-23 to pick up its old route in downtown Ann Arbor.

1965 - A new segment of M-14 freeway opens at Ann Arbor between I-94 at present-day EXIT 171 and Main St (present-day EXIT 3).  M-14 freeway connectors are completed east from US-23 (present-day EXIT 42) and west (present-day EXIT 45), with the three miles in between concurrently designated as US-23/M-14. The M-14 freeway east to I-96/I-275 was not completed until 1979.


Southern Entrance: From Ohio southeast of Ottawa Lake and southwest of Lambertville (17 miles south of Dundee).
Northern Terminus: I-75 at EXIT 338 in Mackinaw City.

In the early days, US-23 between Toledo and Flint was considered somewhat of a "secondary" route. However, it is now one of Michigan's busier freeways through that stretch, carrying traffic around Metro Detroit as well as high levels of Ann Arbor commuter traffic.  According to Ron Willbanks, the original alignment for a US-23 bypass of Ann Arbor was along the present-day routing of Huron Parkway in the eastern portion of the city. This early bypass, proposed in the early 1950s according to Willbanks, would not have been a controlled-access freeway, and if it had been constructed, might have drastically altered the freeway development in the Ann Arbor area. In anticipation of the new "bypass," the University of Michigan purchased a great deal of land in the northwestern portion of Ann Arbor so as to be able to expand their campus toward the new highway. After re-evaluating their plans for freeways around the state in the mid-1950s, Willbanks states that the Dept. of State Highways decided instead to build the current limited-access freeway bypass further away from town in order to have enough room for interchanges and right-of-way. Later, the present-day Huron Parkway was constructed on the proposed US-23 bypass alignment as a four-lane boulevard.

History of US-23:

1958 - A new alignment of US-23 opens from the Huron River north of downtown Ann Arbor to 8 Mile Rd at Whitmore Lake as a limited-access expressway, with some crossroads and a few interchanges.  Part of this would eventually become M-14.

1961 - More construction is completed from the north end of the freeway just north of Milan, around Ann Arbor, connecting with the completed freeway north of Ann Arbor (present-day EXIT 45).  Now, the US-23 designation is transferred to the freeway bypassing Ann Arbor on the east.



Western Entrance: Indiana state line south of New Buffalo
Eastern Terminus: Ontario provincial boundary on the Blue Water Bridge (concurrently with I-69) connecting Port Huron, MI with Sarnia, ON.
Many segments of I-94 were built before the Interstate Highway Bill was signed into law in 1956, and it has begun to show its age.

History of Interstate 94:

1956 - Major changes to US-12 (the future route of I-94) occur during this time frame. A new US-12 southern bypass of Ann Arbor opens to traffic, linking up with the former M-17 and BYP US-112 freeway bypassing Ypsilanti on the south.

1958 - The first I-94 shields appear along the US-12 freeway between Ann Arbor and Detroit.

1962 - The US-23 freeway bypass around Ann Arbor is completed and an interchange is built, with three sides having express-local configurations.



The right of way limits freeway expansion, but an even more important limitation is the width of overpass and underpass structures. At $12,000,000 apiece, these structures are costly and the length of time required to replace them can really snarl traffic for months.  Some overpasses in the system have been replaced and are sufficiently wide to accommodate several additional lanes of traffic.  Bridges over railroads and water are also limiting the width of freeway at certain points, as do wetlands and various hydrological issues.  Some of the structures in the system were built as far back as 1956.  Freeways comparable to the Ann Arbor network, like M-53 in Macomb County, are undergoing extensive freeway deck replacements, despite the fact that these freeways were built in later years (M-53 was completed in 1965).  In addition, several portions of the freeway system have been paved over with asphalt as the original concrete surface deteriorated, and reflectors were not placed in the roadway, making driving during nighttime and inclement weather possibly more hazardous.



Another major concern for this project is to examine what plans the Michigan Department of Transportation (MDOT) has for the freeway system. MDOT has recently published the second edition (2000-2004) of its Five Year Plan for road construction and capital preventive maintenance. Here is a synopsis of MDOT's plans that involve the Ann Arbor freeway system:

In 2000, MDOT completed partial renovation of the M-14 freeway west of the US-23 interchange.  The freeway still includes a stop sign on the Barton Dr. on-ramp but now has a merge and weave lane between that exit and the next.  Shoulders are still nonexistent on the bridge.

MDOT has no plans to make any modifications to I-94 between 2000 and 2005.

In 2005, MDOT plans to replace the US-23 bridges (northbound and southbound) over the Huron River and the Conrail line.




Here is an interesting view of US-23 around the Geddes Rd. interchange, which also includes a bridge over the Huron River and a Conrail line.  The yellow line indicates that the GIS responded that this area has a traffic count over 50,000 vehicles/day.  The lavender line displays the rail line, while the turquoise line shows where the pavement begins and ends.  The area in red represents land parcels, and the area in white is the right of way of US-23. This bridge is scheduled to be replaced in 2005.


This map displays the "questionable parcel" on M-14.  As you can se, the NE corner of this picture seems to show M-14 cutting through a portion of land that somebody owns.  By a field survey, the data is confirmed; the freeway is elevated over a neighborhood.


Note that the above maps clearly delineate where the concrete structures are located.  These concrete structures serve as choke points for road widening purposes.  Because it is not fiscally practical to replace all structures, and because some, like this Nixon Road overpass over US-23/M-14 have been recently rehabilitated, we need to determine how much room is available underneath these structures.  Although the right of way seems adequate for a new structure, it is pragmatic to research whether or not this would be required.



Here is a look at the same site, buffered twelve feet to the outside of the pavement.  The prospects for widening still seem fair, although the incursion into the wetlands is greater, and the possibility of constructing an interchange is severely limited by the fact that the parcels needed to do so are tax-assessed, and therefore owned by someone.  The amount of space present for an interchange is also quite limited, particularly in eastbound access to US-23/M-14.  This map is hampered and must be interpreted with caution because the northwest corner of the map has zero data regarding the right of way present.




First, the database was queried to determine where the traffic count warrants further study.  For purposes of this research, an MDOT traffic count of greater than 50,000 cars per day was selected as the cutoff point.  This is one of the assumptions of my research: a freeway with a traffic count over 50,000 is a candidate for study.  Another assumption or caveat placed on the research is that areas which have had high amounts of recent capital preventive maintenance or reconstruction will not be candidates for development because of the large amounts of money already invested.

Beginning with the US-23 freeway and heading south from M-14, the available right of way was analyzed. Starting with the Plymouth Road intersection, a buffer of 60 feet was drawn around the street centerline.  As you can see, there is some overlap of the two buffers, but ample space exists between the outer limit of the buffers and the concrete structure that holds the overpass deck.  In addition, the buffered area on the entrance and exit ramps, which is admittedly quite excessive, does not touch wetland areas.

Here is an overview of the full interchange site:


Next, examine the area immediately adjacent to the concrete overpass pillars.  There is definitely some overlapping of the buffered area, but it also appears that the edges of the buffers are still a reasonable distance from the concrete pillars.  A shift in the centerline could allow for possible widening (note the measured distance from pillar to buffer).  This is an example of how the researcher used a change in scale to facilitate closer examination and the collection of better data.  Of course, this invites error because the raster view on the screen will not correspond perfectly to reality.



In between Geddes Road and Washtenaw Avenue, the freeway passes over a local road.  The width of the bridge structure is clearly not sufficient and would require an expensive deck replacement.




The next critical interchange where the roadway has a traffic count over 50,000 occurs at Geddes Road.  As you can see, the distance between the pillars is narrower, and seems to prove insufficient for roadway widening.  There also seems to be a problem with wetland mitigation, since the needed space demonstrated by the buffer clearly infringes on wetlands.  Since the bridge over the Huron River and Conrail line is scheduled for replacement in 2005, it might be advantageous to suggest that a deck replacement could be conducted at the same time with minimal impact to traffic, which would already probably be narrowed to one lane each way as the new structures are replaced.  In fact, the construction could deter traffic from avoiding the area altogether.  Finally, an additional merge and weave lane could be added to the new bridge structure to slow traffic down before the Geddes Road off-ramp and prevent some backups onto the freeway proper.

Until we zoom in.  Now, the risk of error is greater, but the digitalized data does give us more of a guide. Still, the freeway right of way over the river, once we remove the wetlands, is evident.  144 feet of space is required to have four lanes in each direction--three through lanes plus a merge/weave lane--exiting onto Geddes northbound, and merging onto the freeway southbound (but the southbound lane could continue all the way to Washtenaw).  Still, with only nine feet of "wiggle room," the tight confines on the right side, construction crews would be hard-pressed to deliver such a bridge structure.


Continuing to travel south of Geddes Road, the freeway has an overpass at Washtenaw Avenue (BUS-94 and M-17).  This too is an overpass with very little right of way, due partially to the cloverleaf structure which takes up much of the right of way.  Also note the wetlands that are within the cloverleaves. 





Proceeding west on Interstate 94, there is a high density traffic area which satisfies the requirements of a traffic count higher than 50,000 until the State Street exit.  Here we will examine the amount of right of way and see if it is sufficient.


One problematic overpass is the Stone School Road overpass.  The section of freeway passing through here has two lanes in each direction, with adequate left and right shoulders.  Since the area is targeted by the GIs as an area with a traffic count higher than 50,000 cars per day, this area should be investigated.  As you will see, the right of way itself is not a limiting factor, but the overpass is too narrow to accommodate further expansion.   The ArcView screen shots below demonstrate the large expansion room and then the narrow confines of the overpass itself.  Buffering 12 feet outside the current roadway, we get this result:


Because of the overwhelming amount of space, another buffer was tried to see if the freeway right of way could possibly accommodate four lanes in each direction, plus left and right shoulders.  The result:


The right of way just seems to touch the wetlands in the upper left corner of the screen shot.  Zoomed in further, we find that the incursion is only about five feet.  This however, does not tell us whether the area is a lake or stream that would have to be crossed, or a wetlands area that might require mitigation.


Conclusive proof: the area is termed "Wetlands" after all.


But, back to the bridge question:  Zooming in, we note that the original 12 foot buffer exceeds the pavement width between the bridge pillars by 12 feet.




West of State Street, the freeway traffic load lightens, presumably because of the high level of commuter traffic coming from the east that exits at State Street.  The next area of study was to examine the possibility of converting the I-94 interchange with M-14 from a partial interchange to a full interchange.  Currently, the interchange only allows eastbound I-94 traffic to access eastbound M-14, and westbound M-14 traffic to access westbound I-94.   This would have two practical applications.  First, it would allow westbound I-94 traffic to exit onto M-14 instead of having to bypass the interchange and then turn around at I-94 exit 169.  Secondly, if we recall that US-23 bridge over the Huron River is to be replaced in 2005, this could provide an alternate freeway route for north  US-23 traffic to follow and still proceed towards Flint and for southbound US-23 traffic to detour around Geddes on the way to Toledo.  The amount of traffic on M-14 east of I-94 is relatively light until the Huron River as well.  Of course, the flip-side of the argument would be that this traffic could contribute to an even higher volume of traffic through a zone that has already been identified as having a traffic count of around 78,000 vehicles/day.  But still, from a research standpoint, the questions are, "Is this possible?" and "If this is possible, it is feasible?"

An overview of the site in question:


The researcher in this case is forced by a lack of data, to assume that the area bordered between the I-94 west to M-14 East ramp and the path of I-94 West is owned by either the state or the county.  If correct, then the study of this interchange involves three research questions.  If the answer to ANY of these is no, then the project would not be feasible.  First, westbound I-94 must have adequate room beneath a local road overpass. Next, the proposed ramp must be possible. Finally, a merge and weave lane must be possible on north M-14.  Does I-94 have adequate room for expansion?  If our assumptions are correct, the answer seems to be yes.



And next, the M-14 underpass. This looks relatively good as well:


The final area of study, completing the loop, is the section of M-14 freeway from roughly Main Street and the Huron River to the US-23/M-14 split.  Much of this freeway was reconstructed in 2000, and therefore, because of the large amount of money, time, and effort expended (about $23,000,000  according to MDOT--see http://www.mdot.state.mi.us/communications/press), this area is not a candidate for further improvements at this time.




The area around the Huron river, however, certainly has its share of accidents, and then some:







Built in 1961, this grade separation allows US-23 traffic to pass over I-94.  Three Here is an overview of the site.  Note the large number of crashes and their placements.  It must be noted that this is 1994 crash data.  Since then, the speed limit of the road has been changed from 55 mph to 70 mph and traffic volumes have increased.


Crash data was obtained from the Southeastern Michigan Council on Governments. It must be noted that the accident data dates from 1994.  It is likely that current data may deviate considerably, as traffic patterns, road conditions, and various other factors (due to deterioration and capital preventive maintenance) have changed in the last six years.  It is, therefore, explicitly assumed that the patterns from 1994 will be reflective of the true situation in 2000.  It is quite possible that we might see a very different pattern in some specific areas.  Those concerns notwithstanding, Ann Arbor freeways are relatively safe roads.  Only two fatalities were recorded during 1994 on Ann Arbor freeways, and both of these were on US-23.  One was a single car-pedestrian accident that was the result of alcohol, and the second occurred in the merging zone southbound on US-23 after the I-94 interchange.  

In 1994, the maximum speed limit was 65mph, due to federal law that prohibited states from setting speed limits themselves.  Most areas identified as 65mph zones in 1994 are now currently posted at either 65mph or 70 mph, and compose the overwhelming majority of the Ann Arbor freeway system today.  The areas not posted at 65mph in 1994 include the section of M-14 just north of downtown, which has been precluded from analysis, and the I-94 intersection with US-23.  

In Washtenaw County, there were a total of 6847 accidents.  306 accidents occurred on the Ann Arbor freeway system (including freeway and ramps, but not intersections of off-ramps).  In 65mph speed zones, there was a total of 115 accidents.  33  of these involved injuries.  Although accidents occurred at virtually all parts of the freeway networks, several areas display accident clustering.  Both 55mph zones in 1994 display heavy clustering of accidents.  The most notable of these exists on westbound I-94 at US-23.





Interestingly, a large portion of the crashes occur on westbound I-94 in the merge and weave zone. 

The crashes above resulted in 1 fatality, but this was not within either of the clusters evident above:



The only other fatality on the freeway network:  single car, alcohol involved, north of Plymouth road on southbound US-23.








Even so, the large number of accidents seem to suggest that something could be done to alleviate the toll accidents take on property and people.  Here is one recommendation:




Wetlands, however, would be infringed upon unless the route was planned carefully.


Other Accident Clusters

I-94 between State Street and Ann Arbor-Saline Road exits



The US-23/M-14 segment.  This data may be erroneous and outdated, since the roadway has now been widened from two lanes to three in each direction and resurfaced (1998 project)





Before proceeding to conclusions of the research, several caveats are required. Political issues, resident concerns and opinions, soil types, environmental concerns, and budget shortages would all require mitigation.  Again, the purpose of this project was to merely pinpoint areas that might be good candidates for improvement and to discover how the freeway system evolved.  In addition, the crash data is from 1994, and as mentioned above, should be interpreted with caution.



     The data in this study indicates that the Ann Arbor freeway system is functioning relatively well.  Crash data, and particularly fatality data, do not indicate widespread danger.  Traffic counts suggest a slight overload in certain areas, but are not excessive throughout the system.  Wetland data and parcel data seem to indicate that adequate right of way seems to exist in many areas, but this is balanced by the omnipresent need to make wise decisions so as to minimize the impact on taxpayers.  The ideas proposed below cannot be looked at individually in a vacuum; many of the recommendations play off one another and are mutually supportive.


Based on this project, the researcher recommends the following action:

1.  Revamp the westbound I-94 to US-23 interchange as soon as possible.  Strongly consider reconstructing the interchange to an express-local format to improve safety, accommodate future growth and replace aging structures.  The crash data portion of the research strongly supports a major reconfiguration of the I-94/US-23 interchange.  There are two options for city planners to consider.  One would be a complete reconstruction of the interchange.  This would be extremely costly, would require the purchase of additional land, and would tie up traffic while construction is completed.   A half-way approach would be more cost-effective, buy additional time to acquire more right of way, and still alleviate traffic concerns in the short term.  The I-94 ramp to southbound US-23 should be eliminated, in favor of a ramp that would spike off the ramp to northbound US-23, and then loop around.  This would require several new bridge structures, but would eliminate the need for merging traffic to carefully negotiate exiting traffic, and could allow this merging traffic to join the freeway without causing an excessive need for freeway traffic to change lanes and reduce speeds.

2.  When replacing the US-23 bridges over the Huron River, take advantage of the available right of way to bring the bridge into conformity with state code (left and right shoulders), and consider adding an extra merge lane to each bridge for exiting and entering traffic.  High traffic counts make merging at the interchange somewhat difficult, and this might prevent back-ups.

3.  Widen I-94 eastbound from US-23 to State Street to improve capacity.  The traffic counts here suggest a high level of commuter traffic and Briarwood Mall traffic.  Improving this section might make area businesses more attractive to visit and would take advantage of the public transportation hub on State Street.  The right of way and wetlands issues limit expansion to only one additional lane in each direction.  Even so, three lanes of traffic should easily handle 78,000 vehicles/day.  Beyond State Street, structure replacement would be required, and this may not be economically feasible, particularly given the lower traffic counts.

4.  Consider improvements to the I-94/M-14 interchange, especially in light of the US-23 Huron River bridge replacement. This could provide a safer and more pleasant alternative than routing US-23 through traffic onto Business-23 and clogging the downtown area.  If this occurs, then widening of I-94 west of State Street could be justified, as traffic heading towards Flint would use I-94 and M-14 to avoid construction in 2005. 


The researcher will be discussing the results of research with city officials in an attempt to become better educated about the process of roadway reconstruction and the planning and decision-making processes. Corollary research projects would enhance the effectiveness of this study.  A study of the Ann Arbor street network in general would complement this study, since surface street networks materially.  A county-wide study of the freeways would also be advisable, since controlling access or providing alternative routes can improve efficiency as well.  The researcher wishes concerned parties good luck in achieving their goals regarding the system and welcomes e-mail contact.


Class Web Page: http://www-personal.umich.edu/~hsiehm/gis.html

Web Page of Professor Arlinghaus:  http://www.umich.edu/~sarhaus