4. Traffic Volumes

4.1 Existing (2001) Traffic Volumes

The existing conditions INTEGRATION modelling and traffic operations analysis of the Highway 417 mainline and ramps were based on Fall 2001 traffic volumes. As described in Section 2, the ramp traffic counts were completed in Fall 2001, but the mainline counts were done in Fall 2000. For modelling and analysis, all mainline a.m. and p.m. peak hour volumes were increased by 0.8% to approximate one year of growth and bring them to a 2001 horizon, consistent with the ramp counts. This growth estimate is from MTO's "Ontario ITS Strategies Framework Study and Five Year COMPASS Implementation Plan".

The ramp volumes were used only in combination with adjacent mainline section volumes in the modelling and analysis. Accordingly, the a.m. and p.m. peak hour ramp volumes used in the modelling and analysis are the volumes for the a.m. and p.m. peak hours of the adjacent mainline sections. Using a common time base for the ramp and mainline volumes was necessary to provide a consistent, realistic existing volume scenario.

The a.m. and p.m. peak hour Highway 417 mainline and ramp volumes used in the INTEGRATION modelling and traffic operations analysis of existing conditions are summarized on a schematic diagram in Appendix C.

4.2 Historical Trends

A review of historical Highway 417 mainline traffic volume data was completed to identify past growth trends. Short-term growth trends were assessed on the basis of a comparison of available Fall 1997 inventory counts to the Fall 2000 inventory counts. Long term trends, over a ten-year horizon, were evaluated by comparing published 1990 AADT's to the 2000 AADT estimates developed as part of this study. The data and growth rate results are summarized in Table 4.1.

4.3 Traffic Volume Projections

The TRANS model produces estimates of p.m. peak hour traffic volumes for the roadway links defined within the model. These link volume estimates are typically not used directly in operational analysis because of the following considerations:

• The model is calibrated at a screenline or corridor level, not on a link by link basis. This provides a level of accuracy sufficient for strategic analysis, but variations between individual link volume projections and actual link volumes may be greater than appropriate for operations analysis.
  
• The model provides link volumes for significant highway and regional roads, however, the model does not provide link volume data for all of the links required for a complete operations analysis of the corridor (e.g. local/collector roadways). In the model network, some minor links may be omitted or combined with other links. The model network is sufficiently detailed for strategic level analysis, but operations analysis requires a volume on every roadway link within the Study Area.
  
• The model is not intended to directly produce turning movement volume estimates. Turning movement volumes are essential for the analysis of the ramp terminal intersections.

The detailed traffic volume projections required for operational analysis and modelling were therefore developed by applying traffic growth patterns indicated by the model to the known existing traffic volumes. This methodology produces estimates of future traffic that are consistent with observed traffic volumes and patterns, while reflecting the planned changes in land use and the municipal road network that are included in the travel demand forecasting model.

Table 4.1 - Mainline Volume Growth Trends Analysis

Mainline Section (between interchanges) From - To	AWD 1997	AWD 2000	Average Annual Growth	AADT 1990	AADT 2000	Average Annual Growth
Highway 416 - Richmond Rd.	-	104,470	-	68,650	93,000	3.1%
Richmond Rd. - Pinecrest Rd.*	-	124,500	-	77,600	112,000	3.7%
Pinecrest Rd. - Woodroffe Ave.	-	132,330	-	89,500	118,000	2.8%
Woodroffe Ave. - Maitland Ave.*	141,330	146,700	1.3%	101,600	130,500	2.5%
Maitland Ave. - KirkwoodAve.	-	152,540	-	104,950	136,000	2.6%
Kirkwood Ave. - Island Park Dr.	-	163,060	-	117,050	145,000	2.2%
Island Park Dr. - Parkdale Ave.	-	166,500	-	120,550	148,000	2.1%
Parkdale Ave. - Rochester St.	166,440	171,130	0.9%	127,600	152,500	1.8%
Rochester St. - Bronson Ave.	154,960	158,140	0.7%	117,900	140,500	1.8%
Bronson Ave. - Lyon St.*	149,690	152,600	0.6%	109,075	136,000	2.2%
Lyon St. - Kent St.	-	135,340	-	-	120,500	-
Kent St. - O'Connor St.	-	135,340	-	98,200	120,500	2.1%
O'Connor St. - Metcalfe St.*	-	134,950	-	95,650	120,000	2.3%
Metcalfe St. - Nicholas St.	-	158,510	-	-	141,000	-
Nicholas St. - Vanier Pkwy.	165,540	170,860	1.1%	115,150	152,000	2.8%
Vanier Pkwy. - St. Laurent Blvd.	-	142,210	-	94,450	126,500	3.0%
St. Laurent Blvd. - Ottawa 174 IC*	-	120,600	-	78,100	107,500	3.2%
Ottawa 174 IC - Innes Rd.*	-	74,200	-	46,850	66,000	3.5%
Innes Rd. - Walkley Rd.*	54,850	58,650	2.3%	30,000	52,000	5.7%
Walkley Rd. - Russell Rd.*	-	33,650	-	23,400	30,500	2.7%

* 2000 Inventory Count location

The methodology used to prepare traffic volume projections for 2011 and 2021 was completed in four main steps. These steps are detailed below.

4.3.1 Balance Existing Condition

The Existing Condition (2001) traffic volumes were based on counts conducted on all ramps in Fall 2001 and at eight mainline locations in Fall 2000. Mainline traffic volumes for sections that were not counted were estimated by using the ramp counts to adjust mainline volumes from sections that had been counted.

Under ideal conditions, freeway system volumes should be balanced, that is, the sum of the through and on-ramp traffic at the upstream interchange should match the sum of the through and off-ramp traffic at the downstream interchange. Since various ramp and mainline counts were conducted on different days, this balanced condition was not achieved with the Existing Condition (2001) traffic volumes.

While imbalances in the Existing Condition volumes were not considered significant for the existing conditions analysis, using unbalanced existing volumes as a basis for projections is not desirable. The imbalances were the result of counting procedures; they represent random variations that should not be projected into the future. Applying growth rates to unbalanced volumes could also produce greater volume differences between interchanges in the future horizon years.

To avoid these problems, adjustments were applied to the Existing Conditions volumes to produce balanced 2001 volumes, to be used as the basis for the volume projections. The adjustments were carried out manually, using the following guidelines:

• Minimize the number of mainline volume adjustments. For example, where the volumes in a single mainline section were higher than the volumes in both adjacent mainline sections, the volumes in the section were adjusted downward rather than raising the volumes in both adjacent sections.
  
• Minimize the magnitude of volume changes. Volume fluctuations of ±10% are generally considered to be within the realm of day-to-day variations in an urban commuter corridor. Volume adjustments were generally maintained within this range. Exceptions occurred on mainline sections with high initial imbalances (e.g. between Nicholas Street and Metcalfe Street, westbound, p.m. peak hour) and ramps with low initial volumes.
  
• Where the volume adjustment required at each end of a mainline section is not the same, distribute the difference to all on and off ramps within the section in proportion to their initial volumes.
  
• Check that adjustments do not produce illogical results (e.g. excessively high ramp volumes, reversing observed peak hour flow direction).

The original and balanced Existing Condition mainline and ramp volumes are summarized on schematic spreadsheets in Appendix C. The mainline count locations are indicated on these schematics by "ICS" (inventory count station).

4.3.2 2021 Volume Projections

The TRANS model produced 2021 p.m. peak hour volume projections for all Highway 417 mainline links, most ramps and some crossing arterial roads. Growth rates were calculated by comparing these 2021 volumes to the corresponding volumes in the model output for the 2001 base year.

While 2001 to 2021 growth rates were calculated for each ramp and crossing roadway with volumes assigned by the model for each horizon year, these growth rates were not considered reliable enough for direct use in generating the 2021 traffic volume projections. As stated above, the model is calibrated on a screenline/corridor basis, not link by link. A comparison of the 2001 model traffic assignment with the Existing Conditions volumes confirmed generally good correlation for Highway 417 mainline volumes, but widely varying correlation for the ramp and crossing roadway volumes.

Since the model was found to be well calibrated for screenlines and Highway 417 mainline links, but not for individual ramp and crossing roadway links, only screenline and Highway 417 mainline link growth rates were used to develop the 2021 volume projections. Specifically:

• Highway 417 mainline link growth rates were directly applied to create mainline traffic volume projections;
• For each on ramp, the downstream mainline link growth rate was applied;
• For each off ramp, the upstream mainline link growth rate was applied; and
• For each crossing roadway, a growth rate of 1% per year was applied. This growth rate reflects the average traffic volume growth projected by the TRANS model across screenlines north and south of Highway 417.

Each of the p.m. peak hour volume projections developed by applying these growth rates was multiplied by the existing a.m. peak hour to p.m. peak hour ratio to produce the corresponding a.m. peak hour projection. Due to variations in growth rates and a.m. to p.m. ratios within each interchange and between interchanges, there were minor volume imbalances in the initial 2021 volume projections. The volumes were balanced by distributing the volume differences at each interchange in proportion to existing ramp volumes.

At the Hunt Club Road interchange, the TRANS model ramp volume forecasts were used directly, since there were no existing volumes to which a growth rate could be applied. The a.m. to p.m. ratios used at the Walkley Road and Hunt Club Road interchanges were adjusted to more closely match the existing ratios at the Innes Road interchange, to reflect the travel pattern changes expected with the introduction of the new interchange.

The TRANS model scenario used for the 2021 traffic volume projections included an extension of Nicholas Street south of Highway 417 (the Alta Vista Extension), with the addition of the related ramps to the interchange, to allow all movements. The Nicholas Street interchange modification was not included in the traffic operations modelling and analysis because its geometric characteristics and timing for implementation are unknown, and its preliminary design is beyond the scope of this Study. The effects of the extension are included in the growth rates for the adjacent Highway 417 mainline sections, as they were derived directly from the model mainline link volumes. The traffic volume projections for the Nicholas Street interchange ramps do not include any effects of the extension. The potential impact of the extension on Highway 417 mainline lane requirements is discussed in Section 6.2.4.

The final, balanced 2021 volume projections are summarized in a schematic spreadsheet in Appendix C.

4.3.3 2011 Volume Projections

The City of Ottawa travel demand forecasting model used for the TMP did not provide a 2011 scenario, although population and employment projections are available. The 2011 volumes were therefore developed by interpolation between the balanced Existing Condition (2001) volumes and the 2021 volume projections. The interpolation was based on the City's planned population and employment growth, as summarized in Table 3.1 and Table 3.2, reflecting an assumption that Highway 417 traffic volumes will grow in direct proportion to the combined growth of population and employment. Although using the City's overall population and employment does not capture all of the potential local variations in growth rates, it is considered a reasonable approach for interim horizon planning purposes, in the absence of a detailed travel demand forecasting model. The interpolation calculation is shown in Table 4.2.

Table 4.2 - Population and Employment Data Used for 2011 Volume Projections

	2001	Planned 2011	Growth 2001 - 2011	Planned 2021	Growth 2001 - 2021	% Growth by 2011*
Population	790,535	1,044,950	254,415	1,191,400	400,865	63.5%
Employment	497,726	676,747	179,021	749,129	251,403	71.2%
Total	1,288,261	1,721,697	433,436	1,940,529	652,268	66.5%

* 2001 to 2011 growth divided by 2001 to 2021 growth

As shown by the data in the table, 66.5% of planned growth in combined population and employment from 2001 to 2021 is expected to occur by 2011. The 2011 traffic volume projections were therefore developed by adding 66.5% of the difference between the balanced 2001 and 2021 volumes to the balanced 2001 volumes. The results are summarized on a schematic spreadsheet in Appendix C.

4.3.4 Intersection Volume Projections

Intersection turning movement volume projections were developed for all intersections that did not fail under existing conditions. Analysis of intersections with significant existing operational problems under higher volume future year conditions was not necessary to establish a need for improvements, as the identified problems would only worsen. As part of the next stage of the Class EA process, these intersections will be analyzed under future volume conditions as necessary to determine the effectiveness of proposed improvement alternatives.

Turning movement volume projections for each ramp terminal intersection were developed by calculating the growth between 2001 and each horizon year (2011 and 2021) for each ramp and crossing roadway, then applying these growth rates to the corresponding intersection approaches. The resulting approach volume projections were distributed in proportion to the existing turning movements. Traffic volume growth on approaches other than ramps and crossing roadways was estimated based on the growth of other approaches at the intersection and the characteristics of the approach (i.e. road classification, surrounding land uses, existing volumes, etc.).

Intersection diagrams summarizing the turning movement volume projections for each intersection are provided in Appendix D.

4.3.5 AADT Projections

Annual average daily traffic (AADT) projections for Highway 417 mainline sections and interchange ramps were produced by applying the existing p.m. peak hour to AADT ratio to the 2011 and 2021 p.m. peak hour volume projections. The p.m. peak hour to AADT ratio will probably decrease over time, as peak spreading will produce greater traffic volume increases outside of the peak hour than will occur during the peak hour. Assuming a constant ratio will tend to underestimate the AADT's, but no firm data was available to support the use of an alternative methodology.

The AADT projections are shown graphically in Figure 4.1, and are summarized in tables in Appendix C.

Figure 4.1 - Highway 417 Mainline Current and Projected AADT

Data in table format

4.3.6 Results

A complete summary of the Highway 417 mainline and interchange ramp traffic volume projections for 2011 and 2021 is provided in Appendix C. Appendix D provides the ramp terminal intersection turning movement volume projections.

Figure 4.2 and Figure 4.3 provide a graphical overview of the volume projections for the a.m. and p.m. peak hours, respectively, throughout the Study Area. Each line on the graph represents the two-way peak hour volumes for one of the horizon years; the current (2001) volumes are included for comparison.

Figure 4.2 - Highway 417 Mainline Current and Projected a.m. Peak Hour Two-Way Volumes

Data in table format

Figure 4.3 - Highway 417 Mainline Current and Projected p.m. Peak Hour Two-Way Volumes

Data in table format

The volume patterns indicated on the graphs are consistent with the historical patterns of growth observed in the Study Area: low to moderate growth through the central section, with higher growth towards the east and west ends. In general, the highest growth is anticipated to the west of Maitland Avenue and to the east of Vanier Parkway. This pattern of projected traffic volume growth is consistent with the expected pattern of population and employment growth in the City of Ottawa, as incorporated into the TRANS model.

The traffic volume growth pattern also reflects the capacity constraints of an unimproved Highway 417. Low growth is projected through the already congested central Ottawa section, where there is no reserve capacity available to accommodate significant traffic volume increases. Higher growth is projected in areas that currently experience less or no congestion, where some reserve capacity is available. With increasing travel demand and more sections of Highway 417 reaching capacity, EMME/2 assigns the additional traffic to other facilities, resulting in lower traffic volume growth rates for the affected sections of Highway 417. Growth in demand thus adds to congestion on the City's arterial road network where it cannot be accommodated on Highway 417.

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Contents | Summary | Introduction | Data Collection | Demand Forecasting | Traffic Volumes
INTEGRATION Modelling | Operations Analysis | Safety Review | Conclusions