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Peak Auto Demand Projections

 One of the requirements for a new bridge was to meet the projected demands of additional peak capacity for automobiles in the 20 to 50 year time horizon.  On this page we will provide some background on how these projections have been derived as well as pointing out some alternative ways in which they could be interpreted.  Lastly we will discuss some recent data that we believe has not been adequately considered when relying on these projections

Peak Auto Demand Projections

The Study team used projections in Phase 1 from the City of Ottawa 2008 Transportation Master Plan and these were based on an origin-destination survey from 2005 combined with population and employment projections out to 2031.  That projection assumed a significant increase in the level of transit ridership across the River but even with that assumption, shows a projection for an extra 1600 people to be crossing the Ottawa river by motorized vehicle by 2031 in the morning peak hour. 

By 2012 the results of the 2011 origin-destination survey were released.  These results are used to derive the 2013 update to the Transportation Master Plan.   One side effect of the lengthy process unfolding for the selection of a corridor for a new east end bridge is that opportunities to review more recent traffic results such as this become possible.

The 2011 survey results changed their method of reporting to be based on a peak 2.5 hour period rather than a peak 1-hour period as was done in the 2008 Transportation Master Plan and hence in the Ph1 traffic analysis of the bridge study.  This makes apples-apples comparisons more difficult.

One striking result of the 2011 data is that the total traffic demand (from Gatineau to Ottawa) in this 2.5 hour morning peak period decreased. This is not the best of news for the 2008 Phase 1 study which based much of its justification for a new east end bridge on projected increases in peak period travel.

The following chart is taken from the 2011 origin-destination survey and compares the travel demand between 2005 and 2011.  During that period the travel demand in the peak 2.5hr period in the morning dropped from 43,200 to 38,600 which is a 10.6% drop during a time period when the NCR population grew by 7.2% and the employed population grew by 8.2%.

The following section summarizes the Ph1 analysis which was performed in 2008 (based on 2005 origin-destination survey data.  Remember that the numbers in the 2011 chart above represent a 2.5hr peak period whereas the numbers in the chart below represent a 1hr peak period.  Thus to make apple/apples comparison the numbers below should be multiplied by between 2 and 2.5.   

In the table below the forecast increase in travel demand  from 2008 to 2031 was 43%.  In reality, what happened between 2005 and 2011 it dropped by 10.3%.

Table 1: 2031 Forecasts for Inter-provincial travel (Made in 2008)

The City of Ottawa assumes that the average occupancy per vehicle is 1.2 and that an extra factor for trips across the river for business (as opposed to personal travel purposes) should also be added.  In discussions with the City they indicated this 'business' factor is an additional 9% of trips.

According to these rules then the number of additional cars to get across the river by 2031 compared to 2007 would be:

15,800 (2031 need) - 14,200 (2005 actual) = 1,600 / 1.2 persons per vehicle * 1.09 (business travel)

= 1,453 additional cars to accommodate across the river by 2031.

It is worth asking the question at this point about how much of this additional demand is for crossings in the central and eastern areas of the region which would make use of additional bridge capacity if it was in place.  If we estimate this as 2/3 of this total (ie 1/3 of this additional crossing demand is in the far west of the region and would not compete for usage of  any crossing needs in the east end) then the 2031 demand for an east end crossing is closer to 1453 * 2/3 = 973 cars (per hour in the peak hour).

From the Phase 1 Final report the consultant has presented the following chart tabling the current capacity and utilization of the Ottawa River bridges.

Table 2: Demand and Capacity of Ottawa River bridges


From this chart it can be seen that the Macdonald-Cartier bridge has an unused capacity of 4,724- 4,064 = 661 vehicles per hour.

An estimated additional demand of 973 cars in the peak hour minus existing spare peak capacity of 661 vehicles per hour on the Macdonald-Cartier bridge leaves a 'congestion level' of 312 vehicles which would arrive and have to 'back-up' causing a queue trying to cross this bridge in the peak hour.  

How much additional delay would this surplus demand of 312 cars in the peak hour impose on drivers crossing the Macdonald-Cartier bridge in 2031?  An estimate of this travel delay from the study team would be useful information to have when comparing the benefits of new bridge options with other alternatives.  Would this add 5 minutes to the commute time experiened across the Macdonald-Cartier bridge?  10 minutes?   In comparison, a new bridge would certainly add enough new capacity to reduce the queuing time to 0 but the study team should also factor in any increased commuting times encountered due to the additional congestion caused on Ottawa roads and streets by this new bridge traffic.  Finally this level of 'net benefit' to drivers should
 be compared against the ability of an east end bridge to remove trucks from downtown.  

The phase 1 study projected that the daily trucks through the downtown would grow to 4300 by 2031 and that an east end bridge would reduce this number to 2590 (by attracting away 40% of the total).  It should be noted that 2590 is approximately the number of trucks currently using Ottawa's downtown to cross the Ottawa River.

If these numbers are correct, then one way to compare the impact of an east end bridge compared to another alternative such as a bypass tunnel between the Macdonald-Cartier bridge and the 417 would be as follows:
                            Congestion Delay               Daily Trucks               Daily Trucks
   In Yr 2031:               for cars                        Downtown                  in East End

East End Bridge               none                          2590                           1710
Downtown Tunnel          5-10 minutes                      0                                0

A chart similar to the one presented above is essential in providing the public and future decision makers with clear data enabling them to make an informed decision concerning what is the best overall solution for the National Capital Region.

Finally, there are numerous ways in which peak period commuting challenges can be addressed. These include transit, relocation of work places, shifting of peak period travel, etc. However when it comes to alternatives to moving trucks out of downtown residential areas there are a much more limited set of alternatives available. This is one of the main reasons why it is important to pay more attention on finding a solution to the truck issue as part of this on-going inter-provincial crossings study.

Past Historical Data

The above 2031 projections for peak auto demand are based on City of Ottawa estimates of long term population and employment growth in the National Capital Region.  This is a difficult challenge and yet key decisions regarding an inter-provincial bridge rest on these.

Below we will provide some information that highlights why such projections can be wrong and which should be cause for generating some additional discussion on the topic of just how many additional cars will there be competing to cross the Ottawa River in 2031.

Downsizing of Previous Projections.

These projections are repeated every five years when the Transportation Master Plan and Official Plan are updated.  In the previous version of these plans in 2002 the 2031 projections that were used for interprovincial crossings were as follows:

Table 3: 2021 Forecasts for Inter-provincial travel (made in 2002)

The key number to focus on here in the 2003 plan is the number of person trips by automobile in 2021 of 18,100.  This is to be compared to the same forecast made in the 2008 plan which is 15,800  and that for the year 2031.    In the updated view  traffic levels in 2031 are 13% below what they had been in 2003  forecasted to be in 2021.  The period between 2003 and 2008 was a period of robust economic expansion.

What will be the revised projections in 2013?  We do not know if the Ph2B study transportation analysis which was released in draft form in spring 2012 will be updated based on the 2011 origin-destination survey numbers.  But the following chart from the survey results released in Dec 2012 indicate that over the period 2005 to 2011 the peak inter-provincial traffic demand decreased. During this period the travel demand in the peak 2.5hr period in the morning dropped from 43,200 to 38,600 which is a 10.6% drop during a time period when the NCR population grew by 7.2% and the employed population grew by 8.2%

It would seem wise to not rely too heavily on such projections for decision making purposes for major new road projects until a longer term trend line can be confirmed.

Observed Traffic Counts on Macdonald-Cartier Bridge

The basic premise underlying the proposal to construct a new bridge in the east end is one of continually increasing auto traffic.  There is a reasonable possibility that such continuous increases may not occur in the future as they have in the past.  One way in which this can be observed is looking at measured traffic counts over the last 5-10 years on these bridges.  We have two sources of data on which to rely for this.  

The first is a chart published on the TRANS website. TRANS is a National Capital Region transportation research group consisting of representatives of the Cities of Ottawa & Gatineau as well as the NCC. This chart illustrates changes in traffic counts across major screenlines in the region, including on the inter-provincial bridges.   Below is a small portion of the chart expanded for legibility purposes.  The full document can be viewed here.

The extracted portion of the chart below shows the % change in morning peak period traffic levels on bridge pairs between 2003 and 2006 (a period of economic growth).  For the easternmost bridge pair (Alexandra + Macdonald-Cartier) there appears to be no noticeable (or even a small drop) in traffic using the bridges.  For the bridge pair immediately to the west of downtown (Chaudieres & Portage) there is a much more noticeable decrease in morning peak traffic.

Chart 1: % Change (decline) 2003 to 2006 in 2.5 hour AM Peak Period Travel Across Eastern Bridges

The second source of information that throws some doubt on the assumption of increasing demand for peak period auto traffic across the east end bridges comes from the comprehensive study undertaken in 2009 to determine the feasibility of reducing King Edward Ave from 6 lanes to 5 or 4 lanes.  This study done by Dillon consulting for the City of Ottawa includes the following charts of 10 year historical traffic trends on the Macdonald-Cartier bridge.  It should be noted that over the period of 2002 to 2007 there was an economic expansion occurring.  It should also be noted that beginning in 2011 the Rapibus project will be coming on line in the east of Gatineau and that the decrease in traffic reported in the chart below has occurred even without the benefit of this improved transit environment.

Chart 2:  10 Year Trend of 2.5 Hour AM Peak Period Travel on Macdonald-Cartier Bridge

This is a second piece of current evidence which does not support the assertion that demand for peak auto travel across eastern bridges is on a steadily advancing growth curve.  Yet the primary justification for discounting other options for addressing inter-provincial transportation challenges is projections for significant increases in peak period auto needs.

The NCC led study team needs to recognize the tenuousness of these projections and display a greater willingness to look at a broader range of solutions to the National Capital Region's inter-provincial transportation challenges.