Do Aussies have a lane merging problem?
The statistics say we aren't at the top of our game — and entry ramps could even become shorter all in the name of hastening things up. Read on, as it all makes sense…It's a major bugbear of drivers and riders: people who do not reach the required speed limit when merging onto motorways or major freeways — despite plenty of time to get the job done. And when someone tries to merge at 60km/h on a 90, 100 or 110km/h road, the end result usually isn't pretty.
A report commissioned by Austroads has confirmed the anecdotal anguish has some vindication, with a field study of 20 entry ramps revealing that in all cases bar one the average merge speed onto a motorway was less than the speed limit on the motorway.
In one example, an entry speed of between 50-70km/h onto an entrance ramp 425 metres long saw only an average merge speed of 81.2km/h onto a 90km/h road.
On 90km/h roads, the best merge average speed was 84.1km/h, for 100km/h roads it was 97.5km/h, and for 110km/h roads it was 107.1km/h.
The only site that recorded an average merge speed higher than the speed limit was on an 80km/h road, where the average speed was 95.6km/h.
The shortest entrance ramp was 45m, which recorded a merging average of 83.2km/h, and the longest 425m which recorded an average of 81.2km/h.
See tables below for the full data:
|
Table 4.2: Entry speed, speed limit and average |
Entry speed (km/h) |
Speed limit on freeway (km/h) |
Average merge speed (km/h) |
Difference (km/h) |
Percentage difference |
|
1 |
60–80 |
100 |
87.6 |
12.4 |
12 |
|
2 |
40–60 |
100 |
86.7 |
13.3 |
13 |
|
3 |
50–70 |
110 |
93.7 |
16.3 |
15 |
|
4 |
40–60 |
100 |
88.8 |
11.2 |
11 |
|
5 |
50–70 |
100 |
88 |
12.0 |
12 |
|
6 |
60–80 |
90 |
84.1 |
5.9 |
7 |
|
7 |
30–50 |
90 |
83.2 |
6.8 |
8 |
|
8 |
50–70 |
100 |
95.2 |
4.8 |
5 |
|
9 |
40–60 |
90 |
83.5 |
6.5 |
7 |
|
10 |
50–70 |
90 |
81.2 |
8.8 |
10 |
|
11 |
60–80 |
100 |
93.7 |
6.3 |
6 |
|
12 |
60–80 |
100 |
97.5 |
2.5 |
3 |
|
13 |
50–70 |
100 |
95.6 |
4.4 |
4 |
|
14 |
60–80 |
100 |
96.4 |
3.6 |
4 |
|
16 |
80–100 |
110 |
106.8 |
3.2 |
3 |
|
17 |
40–60 |
80 |
95.6 |
4.4 |
4 |
|
18 |
60–80 |
110 |
107.1 |
2.9 |
3 |
|
19 |
60–80 |
100 |
96.4 |
3.6 |
4 |
|
20 |
60–80 |
100 |
93.4 |
6.6 |
7 |
Normal
0
false
false
false
EN-US
X-NONE
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin-top:0cm;
mso-para-margin-right:0cm;
mso-para-margin-bottom:10.0pt;
mso-para-margin-left:0cm;
line-height:115%;
mso-pagination:widow-orphan;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;
mso-hansi-font-family:Calibri;
mso-hansi-theme-font:minor-latin;
mso-ansi-language:EN-US;
mso-fareast-language:EN-US;}
|
Table 5.4: Entry/merge speed, merge length and |
Average merge speed (km/h) |
Merge length (m) |
Maximum upgrade (%) |
|
1 |
87.6 |
215 |
1.5 |
|
2 |
86.7 |
340 |
3.7 |
|
3 |
93.7 |
420 |
2.2 |
|
4 |
88.8 |
190 |
3.3 |
|
5 |
88 |
225 |
2.6 |
|
6 |
84.1 |
250 |
4.9 |
|
7 |
83.2 |
45 |
6.5 |
|
8 |
95.2 |
310 |
4.3 |
|
9 |
83.5 |
55 |
2.0 |
|
10 |
81.2 |
425 |
6.3 |
|
11 |
93.7 |
270 |
1.7 |
|
12 |
97.5 |
140 |
3.0 |
|
13 |
95.6 |
320 |
1.1 |
|
14 |
96.4 |
270 |
1.5 |
|
16 |
106.8 |
160 |
0.3 |
|
17 |
95.6 |
310 |
0.2 |
|
18 |
107.1 |
215 |
–0.6 |
|
19 |
96.4 |
230 |
–0.1 |
So is the answer shorter entry ramps to increase the haste?
Austroads hasn't directly addressed that question, but in its summary said that "there is also potential for reducing acceleration lengths at entrance ramps to generate capital and operational cost savings, and higher implied acceleration rates may be appropriate for entrance ramps".
The Austroads project was designed to determine:
• Whether the current design guidance on ramp acceleration lengths provided by the Austroads guides are still valid for today’s Australian vehicles; and
• Appropriate acceleration lengths for entrance ramps that take into account suitable grade correction factors that represent a defendable balance between affordability, operational performance and safety.
The report concluded that:
• There is potential for reducing the acceleration lengths at entrance ramps and such reduction is likely to generate significant capital and operational cost savings;
• The practice of using passenger vehicles as design vehicles and not fully catering for heavy vehicles in terms of acceleration length provision is appropriate;
• The adoption of higher implied acceleration rates may be more appropriate in the design of entrance ramps;
• There are other factors affecting vehicle acceleration at entrance ramps that need to be better understood; and
• Additional investigations are necessary to arrive at definitive recommendations.
To read the full report visit https://www.onlinepublications.austroads.com.au/items/AP-R500-15.
Normal
0
false
false
false
EN-US
X-NONE
X-NONE
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-priority:99;
mso-style-parent:"";
mso-padding-alt:0cm 5.4pt 0cm 5.4pt;
mso-para-margin-top:0cm;
mso-para-margin-right:0cm;
mso-para-margin-bottom:10.0pt;
mso-para-margin-left:0cm;
line-height:115%;
mso-pagination:widow-orphan;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;
mso-hansi-font-family:Calibri;
mso-hansi-theme-font:minor-latin;
mso-ansi-language:EN-US;
mso-fareast-language:EN-US;}
Tags
Please see our Editorial Guidelines & Code of Ethics (including for more information about sponsored content and paid events). The information published on this website is of a general nature only and doesn’t consider your particular circumstances or needs.
