Highways Agency

• Contents
• Executive summary
• 1. Introduction
• 2. Data Collected
• 3. Summary of Results
• 4. Conclusion

3. Summary of Results

3.1 Figure 3.1 below summarises the "Before" and "After" ATC information using five day average two-way traffic flows. A summary results table is included in Annex A of this report.

Figure 3.1 - "Before" & "After" ATC Results: 5 Day Average

3.2 Figure 3.1 shows the 24 hour two way traffic flow on the new bypass for an average weekday in September. Following scheme opening on 18th September 2002, around 28,000 - 30,000 vehicles were recorded using the new bypasses at Silverstone and Syresham respectively. This represents a 2,000 increase in the traffic volumes recorded prior to the scheme opening. Traffic volumes are slightly higher (29,800 vehicles) on the section of carriageway bypassing Syresham (Whitfield Turn to Brackley Hatch) compared with Silverstone Bypass (28,000 vehicles).

3.3 Very low traffic volumes (2,630 and 490 vehicles per day) were observed in Silverstone and Syresham respectively in the latter part of September indicating the scheme has been successful in routeing traffic (over 24,000 vehicles) away from the villages.

3.4 Traffic volumes from the Highways Agency permanent count sites on the A43 (T) at Whitfield to the south west of the scheme and Blisworth to the north east of Towcester (refer to Figure 2.1) also demonstrate an increase of 3,000 vehicles in the A43 corridor.

3.5 Daily traffic volumes on the A43 at Whitfield increased by some 3,000 vehicles to 27,700 vehicles per day after scheme opening (13% increase), matched by a 3,000 increase to 34,100 vehicles at Blisworth (a 9% increase). Furthermore, daily traffic levels increased by around 500 vehicles at both Highways Agency sites on the A5 route.

3.6 Additional traffic has also been recorded on the B4524, a parallel route to the A422 from the M40. The daily flow increased by around 800 vehicles per day following scheme opening, which represents a 30% increase.

3.7 From examination of County data, it is evident that traffic levels have decreased on certain roads in the Northamptonshire area. For example:

• There has been a reduction of 570 vehicles per day on the A361 route (parallel to the A43 from junction 11 of the M40 to Daventry);
• There are 600 fewer vehicles on the A422 route (a parallel route from Buckingham to the A5 at Milton Keynes);
• There is a reduction of 150 vehicles per day on the A413 (route from Buckingham joining the A43 to the north east of the scheme and south of Towcester); and
• In total, therefore a reduction of 1,300 vehicles per day has been observed on the parallel roads.

Journey Times

3.8 A summary of the journey times from the "Before" and "After" scheme opening surveys is shown in the table below.

3.9 This table clearly indicates that significant time savings are being observed on the A43 between the junction 10 of the M40 and A5 at Towcester. These savings are around 7 minutes in the northbound direction and up to 10 minutes in the southbound direction, which represents an increase in speeds from around 40kph in all time periods to around 60kph after the road was opened.

Discussion of Results

3.10 The results from traffic counts on the A43 (T) suggest that there has been a redistribution of traffic on roads in the Northamptonshire area following opening of the new bypass and scheme improvements on the A43. An additional 2,000 - 3,000 vehicles have been attracted into the A43 (T) corridor. Around half of these (1,300 vehicles) appear to have been drawn from other County A-roads, evidenced by a decrease in traffic flows on the A361, A422 and A413.

3.11 Whilst it has not been possible to track changes in flow across all possible routes, it is expected that the remainder is a result of a reassignment of long distance traffic. Given the strategic nature of the widening of A43 and the opportunity that the scheme presents for movement between the M1 and M40, some vehicles may potentially re-route onto the A43 from routes such as M42, A46 and even M25.

3.12 This additional traffic drawn into the corridor only equates to around 5% of the daily traffic using the A43, therefore the level of induced traffic (new trip generation) is likely to be minimal.

3.13 Interestingly, the results show a 30% increase in traffic levels on a County B-road, the B4524, following bypass opening. Clearly, the scheme has encouraged a redistribution of trips onto this road, related to improved links to the A43 (T) following construction of a new grade separated junction on the section of bypass around Syresham.

3.14 Traffic volumes observed on the old A43 Brackley Road through Silverstone showed a significant decline, although traffic volumes of 2,630 vehicles per day were observed following scheme opening. As there is no turn onto the A413 south from the northbound A43, it is possible that vehicles are routing via Silverstone to access the A413 southbound.